rest: add DELETE operation to /server endpoint

Expose deletion of rows from "entornos" table via the /server
endpoint using the DELETE http request method.

The expected payload is the server id as a string. For example:

>>>
DELETE /server
{ "id": "4" }

<<<
200 OK

If the specified server is currently associated with any computer
("ordenadores" table) the foreign key contraint (ON DELETE RESTRICT)
will avoid the deletion and the server responds with
400 Bad Request.

>>>
DELETE /server
{ "id": "1" }

<<<
400 Bad Request

0 files changed, 0 insertions, 0 deletions