Add merging of multiple transactions

[VMelnalksnis]

Changes proposed in this pull request:

• Allow merging of multiple source transactions into a single target transaction

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 47.91667% with 25 lines in your changes missing coverage. Please review.

Project coverage is 70.91%. Comparing base (a0810b5) to head (7e4c07a). Report is 1 commits behind head on master.

:white_check_mark: All tests successful. No failed tests found.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1385 +/- ## ========================================== - Coverage 70.91% 70.91% -0.01% ========================================== Files 551 551 Lines 13997 14024 +27 Branches 1072 1077 +5 ========================================== + Hits 9926 9945 +19 - Misses 3708 3713 +5 - Partials 363 366 +3 ``` | [Components](https://app.codecov.io/gh/VMelnalksnis/Gnomeshade/pull/1385/components?src=pr&el=components&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Valters+Melnalksnis) | Coverage Δ | | |---|---|---| | [API](https://app.codecov.io/gh/VMelnalksnis/Gnomeshade/pull/1385/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Valters+Melnalksnis) | `77.88% <60.00%> (-0.04%)` | :arrow_down: | | [UI](https://app.codecov.io/gh/VMelnalksnis/Gnomeshade/pull/1385/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Valters+Melnalksnis) | `61.63% <44.73%> (+0.05%)` | :arrow_up: |

[VMelnalksnis]

Fixed merging scenario in #1352