Smart Contract information endpoint

[lukeromanowicz]

Implement a GET /contracts/:id endpoint that provides information about verified contracts.

❌ If the contract with the id provided in the PATH doesn’t exist or has not been verified, the response will be an error HTTP 404

✅ If the contract has been verified the response will be HTTP 200 with the following content:

verifiedAt: Datetime string
initCallParameters: string
compiler: string
license: string - one of the predefined license codes
ACI: string

Implement additional validation to POST /contracts endpoint:
❌ If the contract has already been verified, the response will be an error HTTP 409.