fix: LTPA cookie extraction should use prefix matching

[wphillipmoore]

Problem

The LTPA integration test is skipped because the MQ developer container "doesn't return LtpaToken2 cookies."

The root cause is that Liberty's MQ REST API uses a cookie name of LtpaToken2_<suffix> by default (where <suffix> is a random value). The code looks for an exact match on LtpaToken2, so it never finds the cookie even though it IS returned.

Solution

1. Change LTPA cookie extraction from exact match to prefix match on LtpaToken2
2. Store the full cookie name (e.g. LtpaToken2_abcdef) alongside the token value
3. Use the stored cookie name when sending the cookie back in subsequent requests
4. Enable the LTPA integration test (remove skip/ignore mechanism)

Acceptance criteria

• Cookie extraction uses prefix matching (LtpaToken2 prefix)
• Full cookie name is stored and used in the Cookie header
• Unit tests cover both exact (LtpaToken2) and suffixed (LtpaToken2_xyz) cookie names
• LTPA integration test is no longer skipped