feat: AWS S3 + Digitalocean Spaces storage modules (#1015)

* Provide basic implementation of AWS S3 storage module

* Abstract S3 Compatible Storage Module logic

* Refactor `getFileExtension()` into the `page` object

* Add implementation for Digitalocean storage module

* Remove accidental `async`/`await` in S3 Storage Module

* Remove argument from the call to `page.getFileExtension()`

https://github.com/Requarks/wiki/pull/1015#discussion_r321990073

server/modules/storage/s3/common.js

@@ -0,0 +1,64 @@
+const S3 = require('aws-sdk/clients/s3')
+
+/* global WIKI */
+
+/**
+ * Deduce the file path given the `page` object and the object's key to the page's path.
+ */
+const getFilePath = (page, pathKey) => {
+  const fileName = `${page[pathKey]}.${page.getFileExtension()}`
+  const withLocaleCode = WIKI.config.lang.namespacing && WIKI.config.lang.code !== page.localeCode
+  return withLocaleCode ? `${page.localeCode}/${fileName}` : fileName
+}
+
+/**
+ * Can be used with S3 compatible storage.
+ */
+module.exports = class S3CompatibleStorage {
+  constructor(storageName) {
+    this.storageName = storageName
+  }
+  async activated() {
+    // not used
+  }
+  async deactivated() {
+    // not used
+  }
+  async init() {
+    WIKI.logger.info(`(STORAGE/${this.storageName}) Initializing...`)
+    const { accessKeyId, secretAccessKey, region, bucket, endpoint } = this.config
+    this.s3 = new S3({
+      accessKeyId,
+      secretAccessKey,
+      region,
+      endpoint,
+      params: { Bucket: bucket },
+      apiVersions: '2006-03-01'
+    })
+    // determine if a bucket exists and you have permission to access it
+    await this.s3.headBucket().promise()
+    WIKI.logger.info(`(STORAGE/${this.storageName}) Initialization completed.`)
+  }
+  async created(page) {
+    WIKI.logger.info(`(STORAGE/${this.storageName}) Creating file ${page.path}...`)
+    const filePath = getFilePath(page, 'path')
+    await this.s3.putObject({ Key: filePath, Body: page.injectMetadata() }).promise()
+  }
+  async updated(page) {
+    WIKI.logger.info(`(STORAGE/${this.storageName}) Updating file ${page.path}...`)
+    const filePath = getFilePath(page, 'path')
+    await this.s3.putObject({ Key: filePath, Body: page.injectMetadata() }).promise()
+  }
+  async deleted(page) {
+    WIKI.logger.info(`(STORAGE/${this.storageName}) Deleting file ${page.path}...`)
+    const filePath = getFilePath(page, 'path')
+    await this.s3.deleteObject({ Key: filePath }).promise()
+  }
+  async renamed(page) {
+    WIKI.logger.info(`(STORAGE/${this.storageName}) Renaming file ${page.sourcePath} to ${page.destinationPath}...`)
+    const sourceFilePath = getFilePath(page, 'sourcePath')
+    const destinationFilePath = getFilePath(page, 'destinationPath')
+    await this.s3.copyObject({ CopySource: sourceFilePath, Key: destinationFilePath }).promise()
+    await this.s3.deleteObject({ Key: sourceFilePath }).promise()
+  }
+}