Add endpoint to set the definition of a spare

[joelvdavies]

The definition of a spare is effectively a list of usage statuses that a spare would have. We need an endpoint that allows the front end to assign this definition. Endpoint should:

• Be a PUT at /settings/spares_definition
• Take a list of usage statuses that constitute a spare e.g.

  {
   "usage_statuses": [
     { "id": "6723a734ae807034e53cdd13" },
     { "id": "6723a734ae807034e53cdd14" }
   ]
  }
  

• Store these usage statuses for later retrieval
  • Use a settings database collection with an _id: "spares_definition"
  • Either store the values like properties or we can insert them later (e.g. aggregation)
• This task should also ensure ensure a usage status cannot be deleted while it is in the definition