docs: added migration section about JWT able to identify subjects usi…

…ng another field than the user ID (#1066)

docs/guides/migration/v2.5.md

@@ -26,3 +26,25 @@ When using the composable `activity.js` from an another composable be aware that
 👉 New `KRequestProgressBar` component to be used in your `App.vue` or equivalent in order to display a progress bar whenever a request to the server is processing.
 
 👉 New `useErrors()` composable to be used in your `App.vue` or equivalent in order to display a notification whenever a request to the server raises an error.
+
+👉 Ability for JWT to target a user using others properties then the user ID, applications should allow this in their authentication configuration.
+
+::: details ⬇️ Example of an authentication configuration to allow JWT identifying a user by email
+```js
+// default.js of your application, assuming your user objects have an email properties
+authentication: {
+	identityFields: ['email'],
+	...
+}
+```
+
+Your JWT can now be issued [as usual](https://kalisio.github.io/skeleton/guides/development/tips.html#personal-access-token) but using a payload like this:
+```json
+{
+  "aud": "kalisio.xyz",
+  "iss": "kalisio",
+  "exp": 1552402010,
+  "sub": "[email protected]"
+}
+```
+:::