Feature/support multiple environment keys (#55)

* add ability to provide azure keys per environment

* add documentation for the azure environment keys

* singleton variable will cause environment issues

* adjust documentation according to new process env vars

README.md

@@ -128,7 +128,7 @@ Example config.js
 
 ```js
 // config.js
-exports = {
+module.exports = {
   // The username that must be provided via HTTP auth when calling the import-map-deployer
   username: "admin",
   // The password that must be provided via HTTP auth when calling the import-map-deployer
@@ -224,18 +224,25 @@ config.json:
 
 Note, that you must have environment variables `AZURE_STORAGE_ACCOUNT` and `AZURE_STORAGE_ACCESS_KEY`, or `AZURE_STORAGE_CONNECTION_STRING` defined for authentication.
 
-config.json:
+If you wish to provide custom authentication keys for specific environments you can provide it also via the keys `azureConnectionString`, `azureAccount` or `azureAccessKey`.
 
-```json
-{
-  "manifestFormat": "importmap",
-  "locations": {
-    "prod": {
-      "azureContainer": "static",
-      "azureBlob": "importmap.json"
-    }
-  }
-}
+**Its not recommended to put authentication keys in code. Always provide them via environment variables.**
+
+config.js:
+
+```js
+module.exports = {
+  manifestFormat: "importmap",
+  locations: {
+    prod: {
+      azureContainer: "static",
+      azureBlob: "importmap.json",
+      azureConnectionString: process.env.AZURE_STORAGE_ACCOUNT_PROD, // optional
+      azureAccount: process.env.AZURE_STORAGE_ACCOUNT_PROD, // optional
+      azureAccessKey: process.env.AZURE_STORAGE_ACCOUNT_PROD, // optional
+    },
+  },
+};
 ```
 
 ### Google Cloud Storage

src/io-methods/azure.js

@@ -3,12 +3,12 @@ const {
   StorageSharedKeyCredential,
 } = require("@azure/storage-blob");
 
-let blobService;
-
-async function createBlobService() {
-  const connectionString = process.env.AZURE_STORAGE_CONNECTION_STRING;
-  const account = process.env.AZURE_STORAGE_ACCOUNT;
-  const accessKey = process.env.AZURE_STORAGE_ACCESS_KEY;
+async function createBlobService(target) {
+  const connectionString =
+    target.azureConnectionString || process.env.AZURE_STORAGE_CONNECTION_STRING;
+  const account = target.azureAccount || process.env.AZURE_STORAGE_ACCOUNT;
+  const accessKey =
+    target.azureAccessKey || process.env.AZURE_STORAGE_ACCESS_KEY;
   if (connectionString) {
     return await BlobServiceClient.fromConnectionString(connectionString);
   } else if (account && accessKey) {
@@ -27,11 +27,6 @@ async function createBlobService() {
   }
 }
 
-async function getBlobService() {
-  blobService = blobService || (await createBlobService());
-  return blobService;
-}
-
 async function streamToString(readableStream) {
   return new Promise((resolve, reject) => {
     const chunks = [];
@@ -47,7 +42,7 @@ async function streamToString(readableStream) {
 
 // Reference: https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/storage/storage-blob#download-a-blob-and-convert-it-to-a-string-nodejs
 exports.readManifest = async function (target) {
-  const blobService = await getBlobService();
+  const blobService = await createBlobService(target);
   const containerClient = blobService.getContainerClient(target.azureContainer);
   const blobClient = containerClient.getBlobClient(target.azureBlob);
 
@@ -59,7 +54,7 @@ exports.readManifest = async function (target) {
 };
 
 exports.writeManifest = async function (target, content) {
-  const blobService = await getBlobService();
+  const blobService = await createBlobService(target);
   const containerClient = blobService.getContainerClient(target.azureContainer);
   const blockBlobClient = containerClient.getBlockBlobClient(target.azureBlob);
   return await blockBlobClient.upload(content, content.length, {