Reindex queuey priority update

[shirey]

Create a new endpoint, PUT /reindex/<entity id>/priority, to work in conjunction with the new entity reindex prioritized queue functionality. This endpoint will take a required json data payload like:

{
   "priority": x
}

where x can be priority level 1, 2, 3.

• If the entity is in queue with the same, newly requested priority, do nothing and return a 200
• If the entity in the queue is at a different priority level, move the entity to the end of the queue and change the priority to the newly requested level
• if the json payload doesn't exist, doesn't contain the "priority" attribute or doesn't contain a priority value of 1, 2 or 3 return a 400
• if the <entity id> does not exist in the reindex queue return a 404