feat: Support OpenAI-compatible embeddings base URL

[BhagyaAmarasinghe]

Summary

• Add EMBEDDING_BASE_URL as an optional config/env/Helm value for EMBEDDING_PROVIDER=openai.
• Wire the base URL through API, worker, and backfill embedding client creation so Hub can target OpenAI-compatible self-hosted embedding runtimes.
• Validate custom base URLs and reject them for non-OpenAI providers.
• Add tests for config normalization/validation, provider validation, and explicit base URL precedence over OPENAI_BASE_URL.

Validation

• go test ./internal/... ./cmd/... ./pkg/...
• make lint GOLANGCI_LINT="$(go env GOPATH)/bin/golangci-lint"
• git diff --cached --check
• helm lint /Users/bhagya/work/formbricks/hub/charts/hub
• helm template hub /Users/bhagya/work/formbricks/hub/charts/hub --set secrets.stringData.DATABASE_URL=postgres://example --set secrets.stringData.API_KEY=test-key

Notes

go test ./... still requires the local integration Postgres on localhost:5432; that dependency was unavailable in this environment, so the DB-backed tests/ package could not be validated locally.

[coderabbitai]

Walkthrough

This change introduces support for configuring a custom base URL for embeddings services. A new optional environment variable EMBEDDING_BASE_URL is added to configuration files and validated through a refactored URL normalization helper. The configuration value is threaded through embedding client initialization in all relevant entry points (API, worker, backfill commands) and wired into the OpenAI client with a new WithBaseURL option. Validation ensures the base URL is only used with the OpenAI provider. Comprehensive tests verify URL normalization, provider-specific restrictions, and explicit base URL precedence over environment variables.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 31.82% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat: Support OpenAI-compatible embeddings base URL' accurately describes the main change—adding support for a configurable base URL for OpenAI-compatible embeddings.
Description check	✅ Passed	The PR description covers the what, how to test, and validation steps. While the checklist is not explicitly marked with checkboxes, the validation section demonstrates testing and confirmation of the changes made.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@internal/service/embedding_client_factory_test.go`:
- Around line 104-114: Add parallel test cases for the "google-gemini" provider
mirroring the existing "google" BaseURL restriction checks in
TestNewEmbeddingClient and TestValidateEmbeddingConfig: create entries using
Provider set to EmbeddingProviderGoogleGemini (or the constant used for
google-gemini), ProviderAPIKey "key", Model "text-embedding-004", BaseURL
"https://embeddings.example.com/v1", and expect wantErr true with errIs
ErrEmbeddingBaseURLUnsupported; place them alongside the existing google case so
both provider variants assert the same BaseURL restriction.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: cc88769e-4305-4916-85a1-91a12b9a2919

📥 Commits

Reviewing files that changed from the base of the PR and between 3d3f819 and fec8e77.

📒 Files selected for processing (11)

• .env.example
• charts/hub/values.yaml
• cmd/api/app.go
• cmd/backfill-embeddings/main.go
• cmd/worker/app.go
• internal/config/config.go
• internal/config/config_test.go
• internal/openai/client.go
• internal/openai/client_test.go
• internal/service/embedding_client_factory.go
• internal/service/embedding_client_factory_test.go

[xernobyl]

LGTM