add partner_email_sync_portal_login

partner_email_sync_portal_login/README.md

@@ -0,0 +1,24 @@
+# Partner Email Sync Portal Login
+
+When the email of a contact that has a **portal user** is changed and saved:
+
+- the user login is updated with the new (normalized) email, and
+- a password reset email is sent to the new address.
+
+A note is posted in the contact chatter with the result.
+
+## Behaviour details
+
+- Only portal users are affected; internal users are never modified.
+- Empty or invalid emails are ignored (login is kept).
+- Changes that only differ in letter case do not trigger anything.
+- If another user already uses the new email as login, the change is
+  blocked with an error message.
+- If the reset email cannot be sent, the login is still updated and the
+  error is recorded in the chatter.
+- From the portal access wizard ("Grant portal access" / "Invite again")
+  the login is synced but no reset email is sent, since the wizard sends
+  its own invitation.
+- Use the context key `skip_portal_login_sync` to disable the behaviour
+  (e.g. in imports).
+- Changing the login closes the user's open sessions.