Added Applications API support (#338).

Author: gmessner

src/main/java/org/gitlab4j/api/Constants.java

@@ -526,4 +526,48 @@ public String toString() {
             return (enumHelper.toString(this));
         }
     }
+
+    /**
+     * Enum for the various Application scope values.
+     */
+    public enum ApplicationScope {
+
+        /**  Access the authenticated user's API */
+        API,
+
+        /** Read the authenticated user's personal information */
+        READ_USER,
+
+        /**  Perform API actions as any user in the system */
+        SUDO,
+
+        /** Allows read-access to the repository */
+        READ_REPOSITORY,
+
+        /** Authenticate using OpenID Connect */
+        OPENID,
+
+        /** Allows read-only access to the user's personal information using OpenID Connect */
+        PROFILE,
+
+        /** Allows read-only access to the user's primary email address using OpenID Connect */
+        EMAIL;
+
+        private static JacksonJsonEnumHelper<ApplicationScope> enumHelper = new JacksonJsonEnumHelper<>(ApplicationScope.class);
+
+        @JsonCreator
+        public static ApplicationScope forValue(String value) {
+            return enumHelper.forValue(value);
+        }
+
+        @JsonValue
+        public String toValue() {
+            return (enumHelper.toString(this));
+        }
+
+        @Override
+        public String toString() {
+            return (enumHelper.toString(this));
+        }
+    }
 }

src/main/java/org/gitlab4j/api/GitLabApi.java

@@ -51,6 +51,7 @@ public String getApiNamespace() {
     private int defaultPerPage = DEFAULT_PER_PAGE;
     private Session session;
 
+    private ApplicationsApi applicationsApi;
     private AwardEmojiApi awardEmojiApi;
     private BoardsApi boardsApi;
     private CommitsApi commitsApi;
@@ -892,6 +893,25 @@ class VersionApi extends AbstractApi {
         return (response.readEntity(Version.class));
     }
 
+    /**
+     * Gets the ApplicationsApi instance owned by this GitLabApi instance. The ApplicationsApi is used
+     * to perform all OAUTH application related API calls.
+     *
+     * @return the ApplicationsApi instance owned by this GitLabApi instance
+     */
+    public ApplicationsApi getApplicationsApi() {
+
+        if (applicationsApi == null) {
+            synchronized (this) {
+                if (applicationsApi == null) {
+                    applicationsApi = new ApplicationsApi(this);
+                }
+            }
+        }
+
+        return (applicationsApi);
+    }
+
     /**
      * Gets the AwardEmojiApi instance owned by this GitLabApi instance. The AwardEmojiApi is used
      * to perform all award emoji related API calls.