add getPurpose to KAAdapter

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 59.39%. Comparing base (3c4c2d3) to head (e7f0d03).

Files	Patch %	Lines
...tility/adapter/dstu3/KnowledgeArtifactAdapter.java	0.00%	1 Missing :warning:
...cqf/fhir/utility/adapter/dstu3/LibraryAdapter.java	0.00%	1 Missing :warning:
...r/utility/adapter/dstu3/PlanDefinitionAdapter.java	0.00%	1 Missing :warning:
...qf/fhir/utility/adapter/dstu3/ValueSetAdapter.java	0.00%	1 Missing :warning:
...r/utility/adapter/r4/KnowledgeArtifactAdapter.java	0.00%	1 Missing :warning:
...ds/cqf/fhir/utility/adapter/r4/LibraryAdapter.java	0.00%	1 Missing :warning:
...fhir/utility/adapter/r4/PlanDefinitionAdapter.java	0.00%	1 Missing :warning:
...s/cqf/fhir/utility/adapter/r4/ValueSetAdapter.java	0.00%	1 Missing :warning:
...r/utility/adapter/r5/KnowledgeArtifactAdapter.java	0.00%	1 Missing :warning:
...ds/cqf/fhir/utility/adapter/r5/LibraryAdapter.java	0.00%	1 Missing :warning:
... and 2 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #447 +/- ## ============================================ - Coverage 59.44% 59.39% -0.05% Complexity 3189 3189 ============================================ Files 322 322 Lines 16552 16564 +12 Branches 2571 2571 ============================================ Hits 9839 9839 - Misses 5599 5611 +12 Partials 1114 1114 ```

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[TahaAttari]

superseded by #469