Read login_name and display_name back for service users

[jacodegroothydrab]

fetch_user discards login_name and display_name for TYPE = SERVICE:

if user_type != "SERVICE":
    display_name = data["display_name"]
    login_name = data["login_name"]
    must_change_password = data["must_change_password"] == "true"

SHOW USERS has already returned both. The provider reports None regardless, so a config declaring either gets a diff that can never converge — applying it changes nothing and the next plan proposes it again.

Only must_change_password is genuinely unreadable for a service user, so that stays blanked.

It also defeats the point of declaring login_name: ALTER USER ... RENAME TO leaves LOGIN_NAME behind, and a field always read as None cannot surface that drift.

6 unit tests, which fetch_user had none of. Reverting the fix fails one of them.

🤖 Generated with Claude Code

[noel]

The fetch_user change looks correct, including SERVICE, LEGACY_SERVICE, empty-value normalization, and retaining must_change_password behavior.

The branch now conflicts with current main in tests/test_data_provider.py, where this PR and PR #69 appended tests at the same location. Please rebase onto main, retain both test blocks, and rerun the suite.

Please also shorten the seven-line rationale above the changed fetch_user fields to the invariant that matters—for example, # SERVICE users do not report must_change_password. The PR description and tests already preserve the rest of that history. The TestFetchUserServiceFields class docstring can likewise be removed.

[jacodegroothydrab]

Rebased onto main — the conflict in tests/test_data_provider.py was #69's block and this one appended at the same spot, so both are retained. Suite reruns clean (2180 passed; the 6 remaining failures are the pre-existing Windows-only SecurePath/chmod ones, identical on a clean checkout).

Trimmed the rationale to # SERVICE users do not report must_change_password., sitting on the one line it explains, and dropped the TestFetchUserServiceFields docstring.