Fixed configure method for non-refreshable tokens (#526)

## What changes are proposed in this pull request?

We recently added support for disabling auto token refresh
(#525). The
current code is hardcoded to handle refreshable tokens, and it
forcefully refreshes the token on every call of `configure()`
This PR proposed using a token (no matter if it is refreshable or not)
if it is valid. Once the ExternalBrowserCredentialsProvider is run, it
stores the token on disk. If the application is run again, it checks the
token and tries to use it.

## How is this tested?

Added Unit tests

NO_CHANGELOG=true

Author: Divyansh-db

databricks-sdk-java/src/main/java/com/databricks/sdk/core/oauth/ExternalBrowserCredentialsProvider.java

@@ -67,7 +67,7 @@ public OAuthHeaderFactory configure(DatabricksConfig config) {
 
       // First try to use the cached token if available (will return null if disabled)
       Token cachedToken = tokenCache.load();
-      if (cachedToken != null && cachedToken.getRefreshToken() != null) {
+      if (cachedToken != null) {
         LOGGER.debug("Found cached token for {}:{}", config.getHost(), clientId);
 
         try {
@@ -84,9 +84,10 @@ public OAuthHeaderFactory configure(DatabricksConfig config) {
 
           CachedTokenSource cachedTokenSource =
               new CachedTokenSource.Builder(tokenSource)
+                  .setToken(cachedToken)
                   .setAsyncDisabled(config.getDisableAsyncTokenRefresh())
                   .build();
-          LOGGER.debug("Using cached token, will immediately refresh");
+          LOGGER.debug("Using cached token, will refresh if necessary");
           cachedTokenSource.getToken();
           return OAuthHeaderFactory.fromTokenSource(cachedTokenSource);
         } catch (Exception e) {

databricks-sdk-java/src/test/java/com/databricks/sdk/core/oauth/ExternalBrowserCredentialsProviderTest.java

@@ -246,83 +246,127 @@ void sessionCredentials() throws IOException {
   // Token caching tests
 
   @Test
-  void cacheWithValidTokenTest() throws IOException {
-    // Create mock HTTP client for token refresh
+  void cacheWithValidRefreshableTokenTest() throws IOException {
+    // Create mock HTTP client (shouldn't be called for valid token).
     HttpClient mockHttpClient = Mockito.mock(HttpClient.class);
-    String refreshResponse =
-        "{\"access_token\": \"refreshed_access_token\", \"token_type\": \"Bearer\", \"expires_in\": \"3600\", \"refresh_token\": \"new_refresh_token\"}";
-    URL url = new URL("https://test.databricks.com/");
-    Mockito.doAnswer(invocation -> new Response(refreshResponse, url))
-        .when(mockHttpClient)
-        .execute(any(Request.class));
 
-    // Create an valid token with valid refresh token
+    // Create a valid token with valid refresh token (expires in 1 hour - FRESH state).
     Instant futureTime = Instant.now().plusSeconds(3600);
     Token validToken = new Token("valid_access_token", "Bearer", "valid_refresh_token", futureTime);
 
-    // Create mock token cache that returns the valid token
+    // Create mock token cache that returns the valid token.
     TokenCache mockTokenCache = Mockito.mock(TokenCache.class);
     Mockito.doReturn(validToken).when(mockTokenCache).load();
 
-    // Create config with HTTP client and mock token cache
+    // Create config with HTTP client and mock token cache.
     DatabricksConfig config =
         new DatabricksConfig()
             .setAuthType("external-browser")
             .setHost("https://test.databricks.com")
             .setClientId("test-client-id")
             .setHttpClient(mockHttpClient);
 
-    // We need to provide OIDC endpoints for token refresh
+    // We need to provide OIDC endpoints.
     OpenIDConnectEndpoints endpoints =
         new OpenIDConnectEndpoints(
-            "https://test.databricks.com/token", "https://test.databricks.com/authorize");
+            "https://test.databricks.com/oidc/v1/token",
+            "https://test.databricks.com/oidc/v1/authorize");
 
-    // Create our provider with the mock token cache and mock the browser auth method
+    // Create our provider with the mock token cache.
     ExternalBrowserCredentialsProvider provider =
         Mockito.spy(new ExternalBrowserCredentialsProvider(mockTokenCache));
 
-    // Spy on the config to inject the endpoints
+    // Spy on the config to inject the endpoints.
     DatabricksConfig spyConfig = Mockito.spy(config);
     Mockito.doReturn(endpoints).when(spyConfig).getOidcEndpoints();
 
-    // Configure provider
+    // Configure provider.
     HeaderFactory headerFactory = provider.configure(spyConfig);
+    assertNotNull(headerFactory, "HeaderFactory should be created");
 
-    // Verify headers contain the refreshed token even though the cached token is valid
+    // Verify headers contain the CACHED valid token (no refresh needed!).
     Map<String, String> headers = headerFactory.headers();
-    assertEquals("Bearer refreshed_access_token", headers.get("Authorization"));
+    assertEquals(
+        "Bearer valid_access_token",
+        headers.get("Authorization"),
+        "Should use cached valid token without refreshing");
 
     // Verify token was loaded from cache
     Mockito.verify(mockTokenCache, Mockito.times(1)).load();
 
-    // Verify HTTP call was made to refresh the token
-    Mockito.verify(mockHttpClient, Mockito.times(1)).execute(any(Request.class));
+    // Verify NO HTTP call was made (token is still valid, no refresh needed).
+    Mockito.verify(mockHttpClient, Mockito.never()).execute(any(Request.class));
 
-    // Verify performBrowserAuth was NOT called since refresh succeeded
+    // Verify performBrowserAuth was NOT called since cached token is valid.
     Mockito.verify(provider, Mockito.never())
         .performBrowserAuth(
             any(DatabricksConfig.class),
             any(String.class),
             any(String.class),
             any(TokenCache.class));
 
-    // Verify token was saved back to cache
-    Mockito.verify(mockTokenCache, Mockito.times(1)).save(any(Token.class));
+    // Verify token was NOT saved back to cache (we're using the cached one as-is).
+    Mockito.verify(mockTokenCache, Mockito.never()).save(any(Token.class));
+  }
 
-    // Capture the token that was saved to cache to verify it's the refreshed token
-    ArgumentCaptor<Token> tokenCaptor = ArgumentCaptor.forClass(Token.class);
-    Mockito.verify(mockTokenCache).save(tokenCaptor.capture());
-    Token savedToken = tokenCaptor.getValue();
+  @Test
+  void cacheWithValidNonRefreshableTokenTest() throws IOException {
+    // Create mock HTTP client (shouldn't be called for valid token).
+    HttpClient mockHttpClient = Mockito.mock(HttpClient.class);
 
-    // Verify the saved token contains the refreshed values from the HTTP response
-    assertEquals(
-        "refreshed_access_token",
-        savedToken.getAccessToken(),
-        "Should save refreshed access token to cache");
+    // Create a valid token WITHOUT refresh token (expires in 1 hour - FRESH state).
+    Instant futureTime = Instant.now().plusSeconds(3600);
+    Token validTokenNoRefresh = new Token("valid_access_token", "Bearer", null, futureTime);
+
+    // Create mock token cache that returns the valid token.
+    TokenCache mockTokenCache = Mockito.mock(TokenCache.class);
+    Mockito.doReturn(validTokenNoRefresh).when(mockTokenCache).load();
+
+    // Create config with HTTP client and mock token cache.
+    DatabricksConfig config =
+        new DatabricksConfig()
+            .setAuthType("external-browser")
+            .setHost("https://test.databricks.com")
+            .setClientId("test-client-id")
+            .setHttpClient(mockHttpClient);
+
+    // We need to provide OIDC endpoints.
+    OpenIDConnectEndpoints endpoints =
+        new OpenIDConnectEndpoints(
+            "https://test.databricks.com/oidc/v1/token",
+            "https://test.databricks.com/oidc/v1/authorize");
+
+    // Create our provider with the mock token cache.
+    ExternalBrowserCredentialsProvider provider =
+        Mockito.spy(new ExternalBrowserCredentialsProvider(mockTokenCache));
+
+    // Spy on the config to inject the endpoints.
+    DatabricksConfig spyConfig = Mockito.spy(config);
+    Mockito.doReturn(endpoints).when(spyConfig).getOidcEndpoints();
+
+    // Configure provider.
+    HeaderFactory headerFactory = provider.configure(spyConfig);
+    assertNotNull(headerFactory, "HeaderFactory should be created");
+
+    // Verify headers contain the cached token (NOT browser auth!).
+    Map<String, String> headers = headerFactory.headers();
     assertEquals(
-        "new_refresh_token",
-        savedToken.getRefreshToken(),
-        "Should save new refresh token to cache");
+        "Bearer valid_access_token",
+        headers.get("Authorization"),
+        "Should use cached valid token even without refresh token");
+
+    // Verify token was loaded from cache.
+    Mockito.verify(mockTokenCache, Mockito.times(1)).load();
+
+    // Verify NO HTTP call was made (token is still valid, no refresh needed).
+    Mockito.verify(mockHttpClient, Mockito.never()).execute(any(Request.class));
+
+    // Verify performBrowserAuth was NOT called.
+    Mockito.verify(provider, Mockito.never())
+        .performBrowserAuth(any(DatabricksConfig.class), any(), any(), any(TokenCache.class));
+
+    // Verify no token was saved (we're using the cached one as-is).
+    Mockito.verify(mockTokenCache, Mockito.never()).save(any(Token.class));
   }
 
   @Test
@@ -356,7 +400,8 @@ void cacheWithInvalidAccessTokenValidRefreshTest() throws IOException {
     // We need to provide OIDC endpoints for token refresh
     OpenIDConnectEndpoints endpoints =
         new OpenIDConnectEndpoints(
-            "https://test.databricks.com/token", "https://test.databricks.com/authorize");
+            "https://test.databricks.com/oidc/v1/token",
+            "https://test.databricks.com/oidc/v1/authorize");
 
     // Create our provider with the mock token cache
     ExternalBrowserCredentialsProvider provider =
@@ -455,7 +500,8 @@ void cacheWithInvalidAccessTokenRefreshFailingTest() throws IOException {
     // We need to provide OIDC endpoints for token refresh attempt
     OpenIDConnectEndpoints endpoints =
         new OpenIDConnectEndpoints(
-            "https://test.databricks.com/token", "https://test.databricks.com/authorize");
+            "https://test.databricks.com/oidc/v1/token",
+            "https://test.databricks.com/oidc/v1/authorize");
 
     // Create our provider and mock the browser auth method
     ExternalBrowserCredentialsProvider provider =