Fix WithParam RejectOnMatch inverting the match result #1496

[Bafyn]

Problem

WithParam(key, MatchBehaviour.RejectOnMatch, values) returns the opposite result: a request whose param value equals the reject value matches (should be rejected), and a different value doesn't match (should be accepted). AcceptOnMatch is unaffected.

Cause

RequestMessageParamMatcher's params string[] values ctor injects matchBehaviour into each inner ExactMatcher (which already runs MatchBehaviourHelper.Convert), and GetMatchingScore runs Convert again on the aggregate - so it's applied twice.

Fix

Create the inner ExactMatcher with AcceptOnMatch; the behaviour is now applied once by GetMatchingScore. AcceptOnMatch output is unchanged.

Tests

• Unit: RequestMessageParamMatcherTests => RejectOnMatch match/non-match (+ignoreCase) and AcceptOnMatch regressions.
• E2E: WireMockServerTests.WithParam: ?k=abc => 404, ?k=xyz => 200.

References

Fixes #1496

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