[AAE-2718] List available roles for a group (#5954)

* oath2 api service, cleanup identity users service

* cleanup groups service

* get awailable role mappings

* cleanup tests and mocks

* fix lint

lib/core/services/oauth2.service.ts

@@ -0,0 +1,84 @@
+/*!
+ * @license
+ * Copyright 2019 Alfresco Software, Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Injectable } from '@angular/core';
+import { AlfrescoApiService } from './alfresco-api.service';
+import { Observable, from } from 'rxjs';
+
+export const JSON_TYPE = ['application/json'];
+
+export interface OAuth2RequestParams {
+    url: string;
+    httpMethod?: string;
+    pathParams?: any;
+    queryParams?: any;
+    bodyParam?: any;
+}
+
+@Injectable({ providedIn: 'root' })
+export class OAuth2Service {
+    constructor(private alfrescoApiService: AlfrescoApiService) {}
+
+    get apiClient() {
+        return this.alfrescoApiService.getInstance().oauth2Auth;
+    }
+
+    request<T>(opts: OAuth2RequestParams): Observable<T> {
+        return from(
+            this.apiClient.callCustomApi(
+                opts.url,
+                opts.httpMethod,
+                opts.pathParams,
+                opts.queryParams,
+                {},
+                {},
+                opts.bodyParam,
+                JSON_TYPE,
+                JSON_TYPE,
+                Object
+            )
+        );
+    }
+
+    get<T>(opts: OAuth2RequestParams): Observable<T> {
+        return this.request({
+            ...opts,
+            httpMethod: 'GET'
+        });
+    }
+
+    put<T>(opts: OAuth2RequestParams): Observable<T> {
+        return this.request({
+            ...opts,
+            httpMethod: 'PUT'
+        });
+    }
+
+    post<T>(opts: OAuth2RequestParams): Observable<T> {
+        return this.request({
+            ...opts,
+            httpMethod: 'PUT'
+        });
+    }
+
+    delete<T>(opts: OAuth2RequestParams): Observable<T> {
+        return this.request({
+            ...opts,
+            httpMethod: 'DELETE'
+        });
+    }
+}