Added test cases for call token exchange

Author: pmathew92

auth0/src/main/java/com/auth0/android/authentication/AuthenticationAPIClient.kt

@@ -714,7 +714,7 @@ public class AuthenticationAPIClient @VisibleForTesting(otherwise = VisibleForTe
      * Example usage:
      *
      * ```
-     * client.callTokenExchange("{subject token type}", "{subject token}")
+     * client.customTokenExchange("{subject token type}", "{subject token}")
      *       .validateClaims() //mandatory
      *       .setScope("{scope}")
      *       .setAudience("{audience}")
@@ -728,7 +728,7 @@ public class AuthenticationAPIClient @VisibleForTesting(otherwise = VisibleForTe
      * @param subjectToken   the subject token, typically obtained through the Identity Provider's SDK
      * @return a request to configure and start that will yield [Credentials]
      */
-    public fun callTokenExchange(
+    public fun customTokenExchange(
         subjectTokenType: String,
         subjectToken: String,
     ): AuthenticationRequest {

auth0/src/test/java/com/auth0/android/authentication/AuthenticationAPIClientTest.kt

@@ -2272,6 +2272,90 @@ public class AuthenticationAPIClientTest {
         assertThat(body, Matchers.hasEntry("token", "refreshToken"))
     }
 
+    @Test
+    public fun shouldCustomTokenExchange() {
+        mockAPI.willReturnSuccessfulLogin()
+        val callback = MockAuthenticationCallback<Credentials>()
+        client.customTokenExchange( "subject-token-type","subject-token")
+            .setScope("openid profile email")
+            .start(callback)
+        ShadowLooper.idleMainLooper()
+        val request = mockAPI.takeRequest()
+        assertThat(
+            request.getHeader("Accept-Language"), Matchers.`is`(
+                defaultLocale
+            )
+        )
+        assertThat(request.path, Matchers.equalTo("/oauth/token"))
+        val body = bodyFromRequest<String>(request)
+        assertThat(body, Matchers.hasEntry("client_id", CLIENT_ID))
+        assertThat(
+            body,
+            Matchers.hasEntry("grant_type", ParameterBuilder.GRANT_TYPE_TOKEN_EXCHANGE)
+        )
+        assertThat(body, Matchers.hasEntry("subject_token", "subject-token"))
+        assertThat(body, Matchers.hasEntry("subject_token_type", "subject-token-type"))
+        assertThat(body, Matchers.hasEntry("scope", "openid profile email"))
+        assertThat(
+            callback, AuthenticationCallbackMatcher.hasPayloadOfType(
+                Credentials::class.java
+            )
+        )
+    }
+
+    @Test
+    public fun shouldCustomTokenExchangeSync() {
+        mockAPI.willReturnSuccessfulLogin()
+        val credentials = client
+            .customTokenExchange("subject-token-type", "subject-token")
+            .setScope("openid profile email")
+            .execute()
+        val request = mockAPI.takeRequest()
+        assertThat(
+            request.getHeader("Accept-Language"), Matchers.`is`(
+                defaultLocale
+            )
+        )
+        assertThat(request.path, Matchers.equalTo("/oauth/token"))
+        val body = bodyFromRequest<String>(request)
+        assertThat(body, Matchers.hasEntry("client_id", CLIENT_ID))
+        assertThat(
+            body,
+            Matchers.hasEntry("grant_type", ParameterBuilder.GRANT_TYPE_TOKEN_EXCHANGE)
+        )
+        assertThat(body, Matchers.hasEntry("subject_token", "subject-token"))
+        assertThat(body, Matchers.hasEntry("subject_token_type", "subject-token-type"))
+        assertThat(body, Matchers.hasEntry("scope", "openid profile email"))
+        assertThat(credentials, Matchers.`is`(Matchers.notNullValue()))
+    }
+
+    @Test
+    @ExperimentalCoroutinesApi
+    public fun shouldAwaitCustomTokenExchnage(): Unit = runTest {
+        mockAPI.willReturnSuccessfulLogin()
+        val credentials = client
+            .customTokenExchange("subject-token-type", "subject-token")
+            .setScope("openid profile email")
+            .await()
+        val request = mockAPI.takeRequest()
+        assertThat(
+            request.getHeader("Accept-Language"), Matchers.`is`(
+                defaultLocale
+            )
+        )
+        assertThat(request.path, Matchers.equalTo("/oauth/token"))
+        val body = bodyFromRequest<String>(request)
+        assertThat(body, Matchers.hasEntry("client_id", CLIENT_ID))
+        assertThat(
+            body,
+            Matchers.hasEntry("grant_type", ParameterBuilder.GRANT_TYPE_TOKEN_EXCHANGE)
+        )
+        assertThat(body, Matchers.hasEntry("subject_token", "subject-token"))
+        assertThat(body, Matchers.hasEntry("subject_token_type", "subject-token-type"))
+        assertThat(body, Matchers.hasEntry("scope", "openid profile email"))
+        assertThat(credentials, Matchers.`is`(Matchers.notNullValue()))
+    }
+
     @Test
     public fun shouldRenewAuthWithOAuthToken() {
         val auth0 = auth0