API-2194 add client credentials grant type

src/main/java/com/bynder/sdk/model/oauth/GrantType.java

@@ -11,7 +11,7 @@
  */
 public enum GrantType {
 
-    AUTHORIZATION_CODE("authorization_code"), REFRESH_TOKEN("refresh_token");
+    AUTHORIZATION_CODE("authorization_code"), REFRESH_TOKEN("refresh_token"), CLIENT_CREDENTIALS("client_credentials");
 
     private final String name;
 

src/main/java/com/bynder/sdk/query/oauth/TokenQuery.java

@@ -34,8 +34,8 @@ public class TokenQuery {
     @ApiField(name = "redirect_uri")
     private URI redirectUri;
     /**
-     * The authorization grant type. Possible values: {@link GrantType#AUTHORIZATION_CODE} and
-     * {@link GrantType#REFRESH_TOKEN}.
+     * The authorization grant type. Possible values: {@link GrantType#AUTHORIZATION_CODE}
+     * ,{@link GrantType#REFRESH_TOKEN} and {@link GrantType#CLIENT_CREDENTIALS}.
      */
     @ApiField(name = "grant_type")
     private GrantType grantType;

src/main/java/com/bynder/sdk/service/oauth/OAuthService.java

@@ -49,6 +49,13 @@ URL getAuthorizationUrl(final String state, final List<String> scopes)
      */
     Observable<Token> getAccessToken(final String code, final List<String> scopes);
 
+    /**
+     * Gets an access token using the client credentials authorization grant.
+     * @param scopes
+     * @return {@link Observable} with {@link Token} information.
+     */
+    Observable<Token> getAccessTokenClientCredentials(final List<String> scopes);
+
     /**
      * Gets a new access token using the refresh token.
      *

src/main/java/com/bynder/sdk/service/oauth/OAuthServiceImpl.java

@@ -98,6 +98,27 @@ public Observable<Token> getAccessToken(final String code, final List<String> sc
         });
     }
 
+    /**
+     * Check {@link OAuthService} for more information.
+     */
+    @Override
+    public Observable<Token> getAccessTokenClientCredentials(final List<String> scopes) {
+        // use grant type client credentials
+        TokenQuery tokenQuery = new TokenQuery(configuration.getOAuthSettings().getClientId(),
+                configuration.getOAuthSettings().getClientSecret(), null,
+                GrantType.CLIENT_CREDENTIALS, String.join(" ", scopes), null);
+
+        Map<String, String> params = queryDecoder.decode(tokenQuery);
+        Observable<Response<Token>> accessTokenObservable = oauthClient.getAccessToken(params);
+
+        return accessTokenObservable.map(response -> {
+            Token token = response.body();
+            token.setAccessTokenExpiration();
+            configuration.getOAuthSettings().setToken(token);
+            return token;
+        });
+    }
+
     /**
      * Check {@link OAuthService} for more information.
      */

src/test/java/com/bynder/sdk/service/oauth/OAuthServiceImplTest.java

@@ -95,6 +95,14 @@ public void getAccessToken() {
         verify(queryDecoder, times(1)).decode(any());
     }
 
+    @Test
+    public void getAccessTokenClientCredentials() {
+        oAuthService.getAccessTokenClientCredentials(EXPECTED_SCOPES);
+
+        verify(oauthClient, times(1)).getAccessToken(anyMap());
+        verify(queryDecoder, times(1)).decode(any());
+    }
+
     @Test
     public void getRefreshToken() {
         oAuthService.refreshAccessToken();