Add support for access tokens using MAS (#83)

* Add support for access tokens using MAS

* use 1.13.0

* Update dependencies

* Harden auth credential selection in matrix link init

Use the same non-empty access-token criterion for auth mode selection and bind the token directly from the branch condition.
Return explicit configuration errors for missing or empty `device_id`/`password` instead of panicking, so invalid auth config fails gracefully.

* Centralize and harden user auth config handling

Move authentication-mode resolution into typed config parsing with ConfigUserAuth,
so downstream login setup consumes validated credentials instead of re-checking raw optional fields.

Enforce explicit password-vs-token selection, validate token/device/user-id requirements in one place,
and normalize empty auth env overrides to unset values for consistent behavior across YAML and environment input.

* Add auth config unit tests

Move auth_config tests into a dedicated cfg test module file to keep production config code compact while preserving behavior coverage. The tests cover password/token mode selection, missing/both auth method rejection, missing device_id, and empty-value handling.

* Use conventional mxlink version requirement

Replace the unconventional wildcard lower-bound expression with a standard semver lower bound for readability and tooling consistency.

---------

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

etc/app/config.yml.dist

@@ -5,8 +5,17 @@ homeserver:
 
 user:
   mxid_localpart: baibot
+
+  # Authentication: set EITHER password OR access_token + device_id.
+  #
+  # Password-based login (traditional homeservers):
   password: baibot
 
+  # Access token login (for MAS/OIDC-enabled homeservers):
+  # Generate a token via: mas-cli manage issue-compatibility-token <username> [device_id]
+  # access_token: null
+  # device_id: null
+
   # The name the bot uses as a display name and when it refers to itself.
   # Leave empty to use the default (baibot).
   name: baibot