fix(API Usage): Allow self-hosted API usage alerts

[emyller]

• I have read the Contributing Guide.
• I have added information to docs/ if required so people know about the feature.
• I have filled in the "Changes" section below.
• I have filled in the "How did you test this code" section below.

Changes

Contributes to https://github.com/Flagsmith/infrastructure/issues/334

Deprecate get_current_api_usage (Influx) in favour of get_total_events_count (Influx/Postgres).

• Introduce new feature get_current_api_usage_deprecated
• Will experiment and clean up with Standardise querying API calls count #6985

This is part of a plan to enable usage alert emails for self-hosted users, by [experimentally] reading usage data from local Postgres instead of InfluxDB — our usage backend in production.

How did you test this code?

Tests incoming as part of a private cloud endeavour.

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3 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
docs	Ignored	Preview	Mar 20, 2026 0:35am
flagsmith-frontend-preview	Ignored	Preview	Mar 20, 2026 0:35am
flagsmith-frontend-staging	Ignored	Preview	Mar 20, 2026 0:35am

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.32%. Comparing base (dcb0a37) to head (fc9e700).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6975      +/-   ##
==========================================
- Coverage   98.32%   98.32%   -0.01%     
==========================================
  Files        1335     1335              
  Lines       49876    49850      -26     
==========================================
- Hits        49039    49013      -26     
  Misses        837      837              

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[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-6975	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api-test:pr-6975	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-6975	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-6975	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-6975	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-6975	Finished ✅	Results ✅

[github-actions]

Playwright Test Results (oss - depot-ubuntu-latest-16)

 10 passed

Details

 10 tests across 7 suites
 9.5 seconds
 fc9e700
 🔄 Run: #15397 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 10 passed

Details

 10 tests across 7 suites
 11.3 seconds
 fc9e700
 🔄 Run: #15397 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 2 passed

Details

 2 tests across 2 suites
 46.3 seconds
 fc9e700
 🔄 Run: #15397 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 3 passed

Details

 3 tests across 3 suites
 1 minute, 11 seconds
 fc9e700
 🔄 Run: #15397 (attempt 1)

[khvn26]

Looks good in principle. I'd love to see more docs on the feature flag usage here (rationale, rollout plan).

[emyller]

Looks good in principle. I'd love to see more docs on the feature flag usage here (rationale, rollout plan).

I've updated the issue description with a [hopefully] clear rollout plan.