test: add missing unit tests for mapper package

[tekenstam]

Summary

Adds 15 new test functions across the pkg/mapper/ package to improve coverage of previously untested code paths.

New file: pkg/mapper/types_test.go

• TestNew_LoggingDisabled — New() with logging disabled sets client and doesn't panic
• TestNewRolesAuthMap / TestNewUsersAuthMap — constructors initialise all fields
• TestRolesAuthMap_String / TestUsersAuthMap_String — String() output contains expected YAML fields
• TestSetters_RolesAuthMap / TestSetters_UsersAuthMap — SetUsername, SetGroups, AppendGroups chaining
• TestWithRetry_SucceedsFirstAttempt — returns result on first successful call
• TestWithRetry_ExhaustsRetries — error wraps "waiter timed out" after N retries

pkg/mapper/configmaps_test.go

• TestCreateAuthMap_AlreadyExists — second CreateAuthMap call on same client returns an error

pkg/mapper/upsert_test.go

• TestMapper_UpsertMultiple_EmptySlices — empty slices are a no-op (configmap unchanged)
• TestMapper_UpsertMultiple_NilInputs — nil slices handled safely, no crash

pkg/mapper/remove_test.go

• TestMapper_RemoveRole_PartialMatchARNOnly — ARN exists but with wrong username → returns error
• TestMapper_RemoveUser_PartialMatchARNOnly — ARN exists but with wrong username → returns error

Test plan

• go test -v ./pkg/mapper/... — all 45 tests pass (was 30)

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.06%. Comparing base (14123df) to head (32f35c4).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #135      +/-   ##
==========================================
+ Coverage   58.70%   60.06%   +1.36%     
==========================================
  Files          12       12              
  Lines         586      586              
==========================================
+ Hits          344      352       +8     
+ Misses        219      215       -4     
+ Partials       23       19       -4     

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