feat: Improve CozyLink typing and add reset() method

In the Flagship app, we want to be able to reset the local PouchDB
files in order to prevent beta testers to be blocked by an erroneous
Pouch replication

To make this possible we want to expose a public method that resets all
the cozy-client's links

packages/cozy-client/src/CozyLink.js

@@ -9,13 +9,37 @@ export default class CozyLink {
     }
   }
 
-  request(operation, result, forward) {
+  /**
+   * Request the given operation from the link
+   *
+   * @param {any} operation - The operation to request
+   * @param {any} result - The result from the previous request of the chain
+   * @param {any} forward - The next request of the chain
+   * @returns {Promise<any>}
+   */
+  async request(operation, result, forward) {
     throw new Error('request is not implemented')
   }
 
-  persistCozyData(data, forward) {
+  /**
+   * Persist the given data into the links storage
+   *
+   * @param {any} data - The document to persist
+   * @param {any} forward - The next persistCozyData of the chain
+   * @returns {Promise<any>}
+   */
+  async persistCozyData(data, forward) {
     throw new Error('persistCozyData is not implemented')
   }
+
+  /**
+   * Reset the link data
+   *
+   * @returns {Promise<any>}
+   */
+  async reset() {
+    throw new Error('reset is not implemented')
+  }
 }
 
 const toLink = handler =>

packages/cozy-client/src/FlagshipLink.js

@@ -14,7 +14,7 @@ export default class FlagshipLink extends CozyLink {
     // does nothing, we don't need any client for this kind of link
   }
 
-  reset() {
+  async reset() {
     // does nothing, we don't need any client for this kind of link
   }
 

packages/cozy-client/src/StackLink.js

@@ -80,7 +80,7 @@ export default class StackLink extends CozyLink {
     this.stackClient = client.stackClient || client.client
   }
 
-  reset() {
+  async reset() {
     this.stackClient = null
   }