Generate unique message for verification

[Reinachan]

Overview issue: #4

The server needs to generate a unique message that the client can create a Kitsu post from. It needs to contain the user ID of the user and either a random string or random series of words. The server needs to remember this message until the verification process is over.

API Specification

This is psuedocode for demonstration

interface Input {
  userId: string;
}

interface Output {
  message: string;
  targetId: string; // the id of the user the post should be targeted at
}