Feature: CLI should be able to accept paths on /payments request

[andrevmatos]

User Story

As Chris, I want to be able to provide a specific route, presence and fee information to the CLI's /payments endpoint, that I managed to construct on my own, and skip SDK from fetching/paying for an automatic request to PFS on its own. It's my problem how to get this data.

The client should be able to receive the paths in this format:

{
  "paths": [
    {
       "route": [<checksum_address>, …],
       "address_metadata": {
          <checksum_address>: <address_metadata>,
          …
      },
      "estimated_fee": <optional fee int>
    }, …
  ]
}

Acceptance criteria

• User can provide its own paths member to CLI's /payments endpoint.

Tasks