//Post
public async Task <OperationModel> AddOperation(OperationModel anOperation)
{
var theOperEntityToAdd = anOperation.ToEntity();
var theMostRecentId = await context.Operation.MaxAsync(i => i.OperationId);
var theOperationGroup = await context.OperationGroup.FirstOrDefaultAsync(i => i.OperGroupId == anOperation.Group.Id);
theOperEntityToAdd.OperationId = theMostRecentId + 1;
theOperEntityToAdd.OperGroup = theOperationGroup;
context.Add(theOperEntityToAdd);
await context.SaveChangesAsync();
return(theOperEntityToAdd.ToModel());
}