feat(login): add status command (#1087) (#1105)

Implements #1087.

Adds `tea login status [<login name>] [-o <format>]`, which verifies the stored token for one or all configured logins and reports:

- login name/URL and default status
- whether the token is valid (via `GET /api/v1/user`)
- auth method and token expiry
- whether the git credential helper is configured

Machine-readable output is available via the usual `-o` formats with fields `name`, `url`, `user`, `valid`, `auth_method`, `token_expiry`, `helper`, and `default`.

Reviewed-on: https://gitea.com/gitea/tea/pulls/1105
Reviewed-by: bircni <bircni@icloud.com>

docs/CLI.md

@@ -109,6 +109,12 @@ Return the stored token for a URL (git credential protocol)
 
 Refresh an OAuth token
 
+### status
+
+Show authentication status for Gitea logins
+
+**--output, -o**="": Output format. (simple, table, csv, tsv, yaml, json)
+
 ## logout
 
 Log out from a Gitea server