Support refresh token with own idP

Author: abelgardep

owncloudComLibrary/src/main/java/com/owncloud/android/lib/common/http/HttpConstants.java

@@ -56,6 +56,7 @@ public class HttpConstants {
     public static final String HEADER_GRANT_TYPE = "grant_type";
     public static final String HEADER_REDIRECT_URI = "redirect_uri";
     public static final String HEADER_CODE_VERIFIER = "code_verifier";
+    public static final String HEADER_REFRESH_TOKEN = "refresh_token";
 
     /***********************************************************************************************************
      ************************************************ CONTENT TYPES ********************************************

owncloudComLibrary/src/main/java/com/owncloud/android/lib/resources/oauth/TokenRequestRemoteOperation.kt

@@ -32,6 +32,7 @@ import com.owncloud.android.lib.common.http.HttpConstants.HEADER_AUTHORIZATION_C
 import com.owncloud.android.lib.common.http.HttpConstants.HEADER_CODE_VERIFIER
 import com.owncloud.android.lib.common.http.HttpConstants.HEADER_GRANT_TYPE
 import com.owncloud.android.lib.common.http.HttpConstants.HEADER_REDIRECT_URI
+import com.owncloud.android.lib.common.http.HttpConstants.HEADER_REFRESH_TOKEN
 import com.owncloud.android.lib.common.http.HttpConstants.HTTP_OK
 import com.owncloud.android.lib.common.http.methods.nonwebdav.PostMethod
 import com.owncloud.android.lib.common.operations.RemoteOperation
@@ -46,7 +47,7 @@ import timber.log.Timber
 import java.net.URL
 
 /**
- * Get OIDC Discovery
+ * Perform token request
  *
  * @author Abel García de Prada
  */
@@ -67,6 +68,7 @@ class TokenRequestRemoteOperation(
                 .add(HEADER_GRANT_TYPE, tokenRequestParams.grantType)
                 .add(HEADER_REDIRECT_URI, tokenRequestParams.redirectUri)
                 .add(HEADER_CODE_VERIFIER, tokenRequestParams.codeVerifier)
+                .add(HEADER_REFRESH_TOKEN, tokenRequestParams.refreshToken.orEmpty())
                 .build()
 
             val postMethod = PostMethod(URL(uriBuilder.toString()), requestBody)

owncloudComLibrary/src/main/java/com/owncloud/android/lib/resources/oauth/params/TokenRequestParams.kt

@@ -28,6 +28,7 @@ class TokenRequestParams(
     val authorizationCode: String,
     val grantType: String,
     val redirectUri: String,
+    val refreshToken: String? = null,
     val codeVerifier: String,
     val clientAuth: String
 )

owncloudComLibrary/src/main/java/com/owncloud/android/lib/resources/oauth/responses/TokenResponse.kt

@@ -34,7 +34,7 @@ data class TokenResponse(
     @Json(name = "expires_in")
     val expiresIn: Int,
     @Json(name = "refresh_token")
-    val refreshToken: String,
+    val refreshToken: String?,
     @Json(name = "token_type")
     val tokenType: String,
     @Json(name = "user_id")