Added support for custom metadata providers

WiP but already open to feedback

server/models/CustomMetadataProvider.js

@@ -0,0 +1,58 @@
+const { DataTypes, Model, Sequelize } = require('sequelize')
+
+class CustomMetadataProvider extends Model {
+  constructor(values, options) {
+    super(values, options)
+
+    /** @type {UUIDV4} */
+    this.id
+    /** @type {string} */
+    this.name
+    /** @type {string} */
+    this.url
+    /** @type {string} */
+    this.apiKey
+  }
+
+  getSlug() {
+    return `custom-${this.id}`
+  }
+
+  toUserJson() {
+    return {
+      name: this.name,
+      id: this.id,
+      slug: this.getSlug()
+    }
+  }
+
+  static findByPk(id) {
+    this.findOne({
+      where: {
+        id,
+      }
+    })
+  }
+
+  /**
+   * Initialize model
+   * @param {import('../Database').sequelize} sequelize 
+   */
+  static init(sequelize) {
+    super.init({
+      id: {
+        type: DataTypes.UUID,
+        defaultValue: DataTypes.UUIDV4,
+        primaryKey: true
+      },
+      name: DataTypes.STRING,
+      url: DataTypes.STRING,
+      apiKey: DataTypes.STRING
+    }, {
+      sequelize,
+      modelName: 'customMetadataProvider'
+    })
+  }
+}
+
+module.exports = CustomMetadataProvider