FM2-640: Add support for Flag resource

[ManojLL]

Description of what I changed

added FHIR flag resource mapping with openmrs patient flags

Issue I worked on

see https://issues.openmrs.org/browse/FM2-640

Checklist: I completed these to help reviewers :)

• My IDE is configured to follow the code style of this project.

  No? Unsure? -> configure your IDE, format the code and add the changes with git add . && git commit --amend

• I have added tests to cover my changes. (If you refactored
  existing code that was well tested you do not have to add tests)

  No? -> write tests and add them to this commit git add . && git commit --amend

• I ran mvn clean package right before creating this pull request and
  added all formatting changes to my commit.

  No? -> execute above command

• All new and existing tests passed.

  No? -> figure out why and add the fix to your commit. It is your responsibility to make sure your code works.

• My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master

[codecov]

Codecov Report

❌ Patch coverage is 15.38462% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.39%. Comparing base (c7f2ec2) to head (4f734ba).
⚠️ Report is 77 commits behind head on master.

Files with missing lines	Patch %	Lines
...pi/translators/impl/PatientFlagTranslatorImpl.java	6.25%	15 Missing ⚠️
...e/fhir2/providers/r4/FlagFhirResourceProvider.java	16.67%	5 Missing ⚠️
...mrs/module/fhir2/api/dao/impl/FhirFlagDaoImpl.java	33.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #543      +/-   ##
============================================
+ Coverage     77.84%   78.39%   +0.55%     
+ Complexity     2683     2533     -150     
============================================
  Files           239      243       +4     
  Lines          7452     7401      -51     
  Branches        901     1028     +127     
============================================
+ Hits           5801     5802       +1     
+ Misses         1115     1015     -100     
- Partials        536      584      +48     

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