Create Signal Submission API with Validation

[Mathews-25]

Context:
Signal providers submit trade signals with stake verification. The system must validate signal quality, verify on-chain stake, and prevent spam.

Problem:
Build a robust signal submission endpoint that validates data, checks provider stake, and applies quality filters.

What Done Looks Like:

• POST /signals endpoint
• Input validation (prices, rationale length, etc.)
• Stake verification via Soroban smart contract
• Rate limiting per provider
• Signal quality scoring

Folder Structure:

src/
├── signals/
│   ├── signals.controller.ts
│   ├── signals.service.ts
│   ├── validators/
│   │   ├── signal-validator.service.ts
│   │   └── stake-validator.service.ts
│   └── dto/
│       └── create-signal.dto.ts

Implementation Guidelines:

• Validate price logic (target > entry for BUY signals)
• Require minimum rationale length (50 characters)
• Check provider has minimum stake (query Soroban contract)
• Rate limit: 10 signals per provider per day
• Auto-set expiration (24 hours default)
• Generate confidence score based on provider history

Required Fields:

{
  assetPair: string; // e.g., "USDC/XLM"
  action: "BUY" | "SELL";
  entryPrice: number;
  targetPrice: number;
  stopLoss: number;
  rationale: string;
  expiresIn?: number; // hours
}

Edge Cases:

• Provider with insufficient stake
• Invalid asset pair
• Price validation failures
• Duplicate signals within 1 hour

Validation:

• Valid signal created successfully
• Invalid prices rejected
• Stake verification calls Soroban
• Rate limit enforced