[BOUNTY] Create API Documentation with OpenAPI

[HuiNeng6]

Summary

This PR implements comprehensive API documentation for the PrivacyLayer contract as requested in issue #62.

Deliverables

1. OpenAPI Specification (docs/api/openapi.yaml)

• Complete OpenAPI 3.0.3 specification
• All contract endpoints documented:
  • Core Operations: deposit, withdraw
  • View Functions: get_root, deposit_count, is_known_root, is_spent, get_config
  • Admin Functions: initialize, pause, unpause, set_verifying_key
• Request/response schemas
• Error codes and descriptions
• Authentication requirements
• Rate limiting information

2. Contract ABI Documentation (docs/api/CONTRACT_ABI.md)

• All function signatures and parameters
• Data type definitions (Denomination, VerifyingKey, Proof, PublicInputs, PoolConfig)
• Event definitions (DepositEvent, WithdrawEvent, PauseEvent)
• Error codes table
• Gas estimates for each function
• Security considerations
• Integration guide

3. Code Examples

• TypeScript (docs/api/examples/typescript.ts)

  • Full client implementation
  • Deposit and withdraw flows
  • Note management
  • Pool state queries

• Python (docs/api/examples/python.py)

  • Async client implementation
  • All contract interactions
  • Note handling and storage

4. Postman Collection (docs/api/postman_collection.json)

• All API endpoints as request templates
• Environment variables for testnet/mainnet
• Pre-configured examples
• Ready for import and testing

5. Swagger UI (docs/api/swagger-ui.html)

• Interactive API documentation
• Try-it-out functionality
• Custom header with project branding
• Syntax highlighting

Files Changed

• \docs/api/openapi.yaml\ - OpenAPI specification (650+ lines)
• \docs/api/CONTRACT_ABI.md\ - Contract ABI docs (400+ lines)
• \docs/api/examples/typescript.ts\ - TypeScript examples (350+ lines)
• \docs/api/examples/python.py\ - Python examples (500+ lines)
• \docs/api/postman_collection.json\ - Postman collection (550+ lines)
• \docs/api/swagger-ui.html\ - Swagger UI setup

Testing

• OpenAPI spec validates against OpenAPI 3.0.3 schema
• Code examples follow best practices
• Postman collection imports successfully

Related

• Closes [BOUNTY] Create API Documentation with OpenAPI #62
• Bounty: API Documentation with OpenAPI

Payment Address

• USDC (Solana): \9xsvaaYbVrRuMu6JbXq5wVY9tDAz5S6BFzmjBkUaM865\

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Submitted by HuiNeng6