Endpoint: create initial simulation configuration

[jearistiz]

Create a POST request to store the initially minimal simulation configuration document. The request must comply with the following schema:

{
  user_id: ObjectId,
  cmodel_id: ObjectId,
  optimize_parameters: bool
}

In the meantime the backend must store the new simulation configuration in the database with the following fields defined:

{
  simulation_id: ObjectId,
  inserted_at: datetime,
  updated_at: datetime
  user_id: ObjectId,
  cmodel_id: ObjectId,
  optimize_parameters: bool,
  executed: False
}

The HTTP response must comply with:

{
  user_id: ObjectId
  simulation_id: ObjectId
}

This endpoint must be accessed just after the user chooses if the simulation type is optimize parameters or fixed parameters.

[Camilo-HG]

After reviewing the diagram flow, we have noticed that instead of executed it sould be Status and it can take the next values: Incomplete config, Running, Done and Error