add test rule to Makefile and integrate with CI

[idoqo]

This adds support for testing the documentation against the API.
The data sent in the requests are based on the examples we define in our OpenAPI document, for example, given the OpenAPI spec below:

ContactRequest:
  type: object
  description: "Format of the request body for POST/PUT requests to `/contacts` and related sub-paths."
  properties:
    type:
      type: string
      example: "mail"
    value:
      type: string
      example: "devops@example.com"

Schemathesis will generate this request payload:

{
  "type": "mail", 
  "value": "devops@example.com"
}

Schemathesis checks the response code, content type, and the schema of the JSON response.
The test fails if none of it matches what is in the OpenAPI spec.

The request and response body is logged in build/cassette.yml,
and the output is set to verbose mode so all the data can be seen on stdout.

[litleleprikon]

I have a doubts that this tests check the response schemas right. Because in Moira master branch Trigger schema is little bit different than in OpenAPI description. Can you please provide a PR that will proof that schemathesis will fail on incorrect response schema

[litleleprikon]

I think it's better to use this repo instead https://github.com/moira-alert/docker-compose/blob/master/docker-compose.yml

[idoqo]

Don't know if it makes sense, but I was thinking we need to test against the same branch name on main Moira API, for example:
feature/add-teams branch on doc repo should test on feature/add-teams on moira repository.
Because if an API endpoint doesn't exist on master but is documented, then the test will fail (with 404 error)

[idoqo]

feature/add-teams branch on doc repo should test on feature/add-teams on moira repository.

On second thoughts, this brings up the case when the feature is for doc only and doesn't concern the main Moira repo. I think I'd just go ahead and change it to the one you suggested.