Log index validator (#699)

* log index validator - wip

* fix: Handle edge cases in LogIndexValidator and fix GitHub Actions

gix critical edge case: when first transaction has no logs, second transaction starting at logIndex=0 is VALID behavior
 null handling
fix  'repo_token' parameter

* - Use Mono.empty() instead of Mono.just(null)
- Use defaultIfEmpty for handling empty results

* wip : add tests for LogIndexValidator

* test fixes

* fix: Fix ktlint issues in LogIndexValidatorTest

- Remove wildcard import
- Fix trailing spaces
- Add missing trailing commas
- Fix import order
- Add newline at end of file

* add disable option

* add logs for error case

* save prevState on doOnNext

* also check for first tx log index order

* add not continius indexes test

* make code thread safe

* use upstream.getHead

* search CHECK_TX_COUNT instead of 0 and 1 indexes

* refactor double rpc call

.github/workflows/test.yaml

@@ -38,7 +38,7 @@ jobs:
       - name: Setup gradle
         uses: gradle/gradle-build-action@v2
         with:
-          repo_token: ${{ secrets.GITHUB_TOKEN }}
+          github-token: ${{ secrets.GITHUB_TOKEN }}
       - name: Check
         run: make test
         env: