Gateway ext. enhancements | Search by REL Sync strategy performance optimizations

[ndegwamartin]

IMPORTANT: Where possible all PRs must be linked to a Github issue

Resolves #78

Engineer Checklist

• [x] I have written Unit tests for any new feature(s) and edge cases for bug fixes
• [x] I have added documentation for any new feature(s) and configuration option(s) on the README.md
• [x] I have run mvn spotless:check to check my code follows the project's style guide
• [x] I have run mvn clean test jacoco:report to confirm the coverage report was generated at plugins/target/site/jacoco/index.html
• [x] I ran mvn clean package right before creating this pull request.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.02752% with 73 lines in your changes missing coverage. Please review.

Project coverage is 44.30%. Comparing base (712d495) to head (9889c86). Report is 14 commits behind head on main.

Files	Patch %	Lines
...ister/fhir/gateway/plugins/SyncAccessDecision.java	22.36%	56 Missing and 3 partials :warning:
.../fhir/gateway/plugins/PermissionAccessChecker.java	0.00%	6 Missing :warning:
...teway/plugins/LocationHierarchyEndpointHelper.java	76.47%	4 Missing :warning:
...way/plugins/PractitionerDetailsEndpointHelper.java	60.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #79 +/- ## ============================================ - Coverage 45.01% 44.30% -0.72% - Complexity 130 135 +5 ============================================ Files 16 16 Lines 1213 1316 +103 Branches 146 156 +10 ============================================ + Hits 546 583 +37 - Misses 600 667 +67 + Partials 67 66 -1 ```

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