custom program certificates

[muhammadammar-ma]

Summary

• Add database-backed custom program certificate templates, allowing certificate HTML to be managed via Django admin instead of requiring file-based templates deployed with the code
• Introduce CertificateAsset model for uploading and referencing images, fonts, and CSS in certificate templates via a {% certificate_asset_url 'slug' %} template tag
• Gate the feature behind a credentials.custom_program_certificate_templates waffle switch for safe rollout
• Include FBR program certificate template and assets (fonts, logos) as the first use case

Details

New Models

ProgramCertificateTemplate — Stores Django template HTML with optional organization scoping. Template selection follows a priority hierarchy:

1. Active template matching both program certificate + organization (most specific)
2. Active template matching program certificate only (fallback)

Unique constraints enforce a single active template per scope, preventing ambiguous lookups.

CertificateAsset — Stores uploadable files (images, fonts, CSS) identified by a unique slug. Templates reference assets using {% load certificate_assets %}{% certificate_asset_url 'my-slug' %}, which gracefully degrades to an empty string with a logged warning if the slug is missing.

Admin Interface

• ProgramCertificateTemplateAdmin with autocomplete fields, search by org key/program UUID, and fieldsets separating configuration from template HTML editing
• CertificateAssetAdmin with slug-based lookup, read-only asset URL preview, and upload guidance

Feature Toggle

Waffle switch credentials.custom_program_certificate_templates (default: off). When enabled, the rendering path checks for a database template before falling back to file-based templates.

Test plan

• Enable waffle switch credentials.custom_program_certificate_templates
• Create a CertificateAsset via Django admin and verify the upload path and URL preview
• Create a ProgramCertificateTemplate via Django admin with template HTML referencing an asset slug
• Verify program certificate renders using the DB template instead of the file-based one
• Verify org-scoped template takes priority over program-only template
• Disable the waffle switch and verify fallback to file-based templates
• Verify missing asset slugs log a warning and render gracefully (no 500)

[ahmed-arb]

Looks good to me. Could you please add a bit more detailed PR description?