Verification API 2

[FabijanC]

• Changes to Verification API 1:
  • by virtue of returning a better message and/or status code:
    • fixes Handle error when files are provided in different than files parameter in /verify endpoint #339
    • fixes /checkByAddresses API endpoint returns internal server error if no params provided #335
    • fixes Return different status for the already verified contract through /verify API endpoint #334 (response includes storageTimestamp if already verified)
  • so far, all POST requests were handled by the same handler, i.e. a POST request to any of the following would behave the same way: "/verify", "/", "/wild-path", "/another-wild-path"
    • now only "/verify" and "/" are legal Verification API 1 paths for POST requests
• Additions (Verification API 2):
  • session functionality
  • compiler selection (prerequisite for standard JSON)
  • every valid request returns an object with the status of currently pending contracts
• Pending:
  • the light request use-case (the user only wants to check the contract at a given address)
  • standard-json support (this can be included in a separete pull request)
  • discuss the the new endpoint structure (i.e. how the old and the new URL paths should be named), w.r.t. to possible breaking changes
• Changes have been reflected in the documentation (.md files and Postman collection)

_{View in Huly HI-1050}

[DeFiYaco]

Look into this documentation https://express-validator.github.io/docs/
I think you can make these API endpoints cleaner by using this package. We are already using it in the FileController.ts.

Also, there are few TODO comments that I would like you to check out if you forgot about them. We can discuss them if you need help with something.