Gate local repo writes behind OIDC tokens

Add ARTIFACTAPI_AUTH_UPLOADS to require a verified token for local
uploads, deletes, evictions, /api/v1 publishes and /v2 push. Accept the
token as Bearer, Token, Basic password or bare header, and serve a
Docker registry token endpoint so pulls stay anonymous.

docs/ansible/local.md

@@ -2,7 +2,7 @@
 
 A local `ansible` repo is a Galaxy v3 server: `ansible-galaxy collection publish`
 and `ansible-galaxy collection install` work against `/api/v1/local/<repo>`.
-`publish` needs an API key; any value works.
+`publish` needs an API key; any value works unless [uploads are gated](../common/auth.md).
 
 ```bash
 ansible-galaxy collection build