Dropped `age` column from patient registration and annotated age in patient viewset

[rithviknishad]

Proposed Changes

• Dropped DB field age from Patient Registration
• Adds field death_datetime in Patient Registration
• Custom Migration to copy last_consultation's death_datetime to patient registration if present
• Updated consultation save method to update patient registration's death_datetime too if consultation has death_datetime.
• Annotated patient viewset with age to calculate age based on data of birth/year of birth up to date of death or now.

Associated Issue

• https://github.com/coronasafe/care_fe/issues/7383
• FE: https://github.com/coronasafe/care_fe/pull/7411

[!NOTE]

Custom Migrations

• Populates PatientRegistration.death_datetime with instance.last_consultation.death_datetime if present.

Screenshots

POST /api/v1/patient/ - Patient Create's request body:

GET /api/v1/patient/ - Patient List's updated filters and response body:

Merge Checklist

• [ ] Tests added/fixed
• [ ] Update docs in /docs
• [ ] Linting Complete
• [ ] Any other necessary step

Only PR's with test cases included and passing lint and test pipelines will be reviewed

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