feat(COG-146): Add provider availability management backend

[devin-ai-integration]

Summary

Adds full-stack backend support for managing provider scheduling availability. This includes:

• Flyway V3 migration creating provider_availability table with constraints for block types, time ranges, slot durations, and a recurring-vs-specific-date XOR check
• JPA entity (ProviderAvailability) with @ManyToOne to Provider, optimistic locking via @Version, @JsonIgnore on the LAZY provider field, and a @Transient getProviderId() getter for JSON serialization
• DTO with @NotNull validation on required fields
• Repository with derived queries and two custom JPQL queries for effective-date and date-range lookups
• Service with CRUD operations, soft-delete (deactivate), and validation (time ordering, slot duration whitelist, recurring/specific-date constraints)
• Controller at /v1/providers/{providerId}/availability with 8 endpoints (list, get, recurring, by-date, effective, range, create, update, delete) including provider ownership checks
• 15 unit tests covering service validation, CRUD operations, block type enumeration, and effective-date merging

Updates since last revision

• Fixed @Table(indexes=...) to use SQL column names (day_of_week, block_type) instead of Java field names, avoiding potential duplicate-index conflicts with the Flyway migration
• Fixed findEffectiveForDate to copy the JPA-returned list into a new ArrayList before appending overrides, preventing UnsupportedOperationException on unmodifiable lists
• Added ProviderAvailabilityServiceTest with 15 Mockito-based unit tests
• Added @JsonIgnore on the provider field to prevent LazyInitializationException on GET endpoints
• Added @Transient getProviderId() so the JSON response still includes the provider's ID without triggering lazy loading

Review & Testing Checklist for Human

• getProviderId() outside transaction: The @Transient getter calls provider.getId() on a LAZY proxy. Hibernate proxies store the ID without lazy loading, so this should work outside the @Transactional boundary — but verify with a live request that GET responses include providerId correctly and don't throw LazyInitializationException.
• No overlap detection: The service allows creating multiple blocks for the same provider/day/time range. Decide whether overlapping blocks should be rejected or are acceptable.
• JPQL queries untested: The unit tests mock the repository, so the two custom @Query methods (findEffectiveRecurringForDate, findByProviderIdAndDateRange) are not exercised against a real database. Consider adding an integration test with H2 to verify these queries.
• Day-of-week mapping: date.getDayOfWeek().getValue() % 7 maps Sunday→0, Monday→1 ... Saturday→6. Verify this matches the frontend's convention and the chk_day_of_week constraint (0–6).

Suggested test plan: Start the API with a running Postgres instance, execute the Flyway migration, and manually test the CRUD endpoints via curl/Postman. Specifically verify: creating a recurring block, creating a specific-date override, the /effective endpoint returns both, the DELETE endpoint soft-deletes correctly, and that GET responses include providerId in the JSON without errors.

Notes

• DELETE endpoint performs soft-delete (active=false) rather than hard delete — this is intentional
• The BlockType enum is shared with the frontend PR (COG-GTM/demos-coghealth-ehr-web)
• findByProviderIdAndBlockTypeAndActiveTrue is declared in the repository but not currently called by the service or controller — it's available for future use

Link to Devin session: https://app.devin.ai/sessions/f65523f6eeb84bbb9f183b66eea0786a
Requested by: @stephencornwell

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring