feat: #520 add better support for object variables and deserialization

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
:white_check_mark: +0.12%	:white_check_mark: 72.15%

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (169bd9ce3bb2ac321f9c11b17c8f7c94e6a7889f) | 3928 | 2722 | 69.30% | | | Head commit (f86cd86f0b3c73a418734a678d8f8d65ff229320) | 3956 (+28) | 2746 (+24) | 69.41% (**+0.12%**) | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#523) | 79 | 57 | **72.15%** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.54545% with 35 lines in your changes are missing coverage. Please review.

Project coverage is 59.93%. Comparing base (169bd9c) to head (f86cd86).

Files	Patch %	Lines
.../community/rest/variables/ValueTypeResolverImpl.kt	25.00%	3 Missing and 6 partials :warning:
...rg/camunda/community/rest/variables/ValueMapper.kt	50.00%	7 Missing :warning:
...amunda/community/rest/impl/RemoteRuntimeService.kt	70.00%	0 Missing and 6 partials :warning:
...g/camunda/community/rest/impl/RemoteTaskService.kt	33.33%	4 Missing and 2 partials :warning:
...amunda/community/rest/variables/SpinValueMapper.kt	0.00%	3 Missing :warning:
...a/community/rest/impl/RemoteExternalTaskService.kt	60.00%	2 Missing :warning:
...mpl/builder/DelegatingMessageCorrelationBuilder.kt	66.66%	1 Missing :warning:
...da/community/rest/variables/MessageResultMapper.kt	50.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #523 +/- ## ============================================ - Coverage 60.09% 59.93% -0.16% - Complexity 962 965 +3 ============================================ Files 61 61 Lines 3634 3662 +28 Branches 326 344 +18 ============================================ + Hits 2184 2195 +11 - Misses 1121 1126 +5 - Partials 329 341 +12 ```

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[rohwerj]

fixes #520