adding ms grpah client

libs/modules/src/azAppConfig/az-app-config.service.ts

@@ -0,0 +1,55 @@
+import { Inject, Injectable } from '@nestjs/common';
+import { AppConfigOptions } from './az-app-config.interface';
+import { APP_CONFIG_OPTIONS } from './az-app-config.constants';
+import axios, { AxiosResponse } from 'axios';
+import { FeatureFlagValue } from '@azure/app-configuration';
+
+@Injectable()
+export class AppConfigService {
+  constructor(
+    @Inject(APP_CONFIG_OPTIONS)
+    private appConfigOptions: AppConfigOptions
+  ) { }
+
+  async getToken(): Promise<string> {
+    try {
+      const { data }: AxiosResponse = await axios.post(
+        `https://login.microsoftonline.com/${this.appConfigOptions.tenantId}/oauth2/token`,
+        {
+          grant_type: 'client_credentials',
+          client_id: this.appConfigOptions.clientId,
+          client_secret: this.appConfigOptions.clientSecret,
+          resource: 'https://azconfig.io'
+        },
+        {
+          headers: {
+            'Content-Type': 'application/x-www-form-urlencoded'
+          }
+        }
+      );
+
+      return data.access_token;
+    } catch (error) {
+      return error;
+    }
+  }
+
+  async getFeatureFlags(token: string, key: string, label: string): Promise<FeatureFlagValue[]> {
+    try {
+      const token: string = await this.getToken();
+      const response: AxiosResponse = await axios.get(
+        `${this.appConfigOptions.url}/kv?key=.appconfig.featureflag/${key}&label=${label}`,
+        {
+          headers: {
+            Authorization: `Bearer ${token}`
+          }
+        }
+      );
+      const featureFlags: FeatureFlagValue[] = response.data.items.map((item) => JSON.parse(item.value));
+
+      return featureFlags;
+    } catch (error) {
+      return error;
+    }
+  }
+}