`kamu login`: revisit command ergonomics

[s373r]

At the moment, from a UX perspective, we can perform a login in three ways:

1. kamu login password $USER $PASSWORD $KAMU_NODE_URL

• ✅ Password authorization (calls kamu node API)

2. kamu login oauth github $TOKEN $KAMU_NODE_URL

• ✅ OAuth token authorization (calls kamu node API)

3. kamu login --access-token $TOKEN $KAMU_NODE_URL

• :warning: Only saves the received token to a file (.kamu/.kamutokenstore) without API calls

---

As a suggestion: make kamu login --access-token an alias for kamu login oauth github.

This way we will have a single code path to work with the token and the command kamu login (3).) will not be misleading.