[FEATURE] Add collection-level data validation rules — enforce schema constraints (min/max length, regex, required fields) before insert/update

[Abhushan187]

Problem

While urBackend supports unique field constraints (PR #52), there is no way for project owners to enforce data quality rules such as "email must match regex", "username must be 3-20 characters", or "age must be a positive integer". Invalid data enters the database freely, causing application bugs downstream and forcing client-side validation duplication across every SDK consumer.

---

Proposed Improvement

Add per-field validation rules in the collection schema designer that enforce constraints at the API level before any insert or update operation. The feature should:

• Support validation types: minLength, maxLength, min, max, regex, enum, required
• Validate on both POST /api/data/{collection} (insert) and PATCH /api/data/{collection}/{id} (update)
• Return standardized 422 Unprocessable Entity with detailed field-level error messages
• Show validation rules in the dashboard schema designer with live preview
• Apply validation in both public-api and dashboard-api for consistency
• Skip validation for sk_live requests if explicitly configured (admin override)

---

Expected Impact

• Better data quality and integrity across all projects
• Reduced client-side validation duplication in SDKs
• Improved developer experience with clear validation errors
• Better long-term scalability with pluggable validation engine

---

Possible Implementation

• Add ValidationRule schema to packages/common/models/ with fields: type, value, message, fieldId
• Extend Field model with validationRules array
• Add validateDocument middleware in apps/public-api/middleware/ and apps/dashboard-api/middleware/
• Integrate with existing unique constraint flow (PR feat: add unique field constraints support with validation and model … #52) for unified validation pipeline
• Update dashboard UI: add validation rule builder per field type with regex tester
• Add GET /api/projects/{id}/collections/{name}/validation endpoint to fetch rules
• Write tests for each validation type, edge cases (empty string, null, regex edge cases), and bypass scenarios

---

I'm GSSoC'26 contributor, Please assign this task to me!

[Abhushan187]

Problem

While urBackend supports unique field constraints (PR #52), there is no way for project owners to enforce data quality rules such as "email must match regex", "username must be 3-20 characters", or "age must be a positive integer". Invalid data enters the database freely, causing application bugs downstream and forcing client-side validation duplication across every SDK consumer.

---

Proposed Improvement

Add per-field validation rules in the collection schema designer that enforce constraints at the API level before any insert or update operation. The feature should:

• Support validation types: minLength, maxLength, min, max, regex, enum, required
• Validate on both POST /api/data/{collection} (insert) and PATCH /api/data/{collection}/{id} (update)
• Return standardized 422 Unprocessable Entity with detailed field-level error messages
• Show validation rules in the dashboard schema designer with live preview
• Apply validation in both public-api and dashboard-api for consistency
• Skip validation for sk_live requests if explicitly configured (admin override)

---

Expected Impact

• Better data quality and integrity across all projects
• Reduced client-side validation duplication in SDKs
• Improved developer experience with clear validation errors
• Better long-term scalability with pluggable validation engine

---

Possible Implementation

• Add ValidationRule schema to packages/common/models/ with fields: type, value, message, fieldId
• Extend Field model with validationRules array
• Add validateDocument middleware in apps/public-api/middleware/ and apps/dashboard-api/middleware/
• Integrate with existing unique constraint flow (PR feat: add unique field constraints support with validation and model … #52) for unified validation pipeline
• Update dashboard UI: add validation rule builder per field type with regex tester
• Add GET /api/projects/{id}/collections/{name}/validation endpoint to fetch rules
• Write tests for each validation type, edge cases (empty string, null, regex edge cases), and bypass scenarios

---

I'm GSSoC'26 contributor, Please assign this task to me!

/assign