feat: Add database replica URLs

[rolodato]

Changes

Do not release until Flagsmith/flagsmith#5222 is released.

Adds support for defining replicas using the databaseExternal.replicas.databases and databaseExternal.crossRegionReplicas.databases values. We accept the same formats as databaseExternal for the primary database (plaintext URL, key/value components, or secret reference).

Also removes the E2E tests from this repository, since they're testing things outside the scope of the Helm chart. We can add Helm-specific tests if we need to, such as the ones added by this PR.

How did you test this code?

Helm tests.

[rolodato]

Confirmed these tests are running and passing in CI - see https://github.com/Flagsmith/flagsmith-charts/actions/runs/13819367403/job/38660668849?pr=337#step:9:2399

[khvn26]

I'm curious we're testing integrated postgres enabled + replicas and not external postgres + replicas here.

[rolodato]

The dev postgres is only so that there's an actual database we can use while running the tests. If we remove this, or refer to a non-existing external database, the API containers cannot come up and the tests fail.

In any case, we're not testing anything relating to the primary database (integrated or external). We're only testing that if you pass in the Helm values for replicas in different formats, then the API containers will have the correct environment variables set on them.

[rolodato]

Tests are passing and this is ready to ship: https://github.com/Flagsmith/flagsmith-charts/actions/runs/16151118638/job/45582380606?pr=337#step:9:267

@khvn26 could you have another pass at this when you have the chance?

[matthewelwell]

I don't think that we should merge this until we have a solution to this issue.