API call /maintenance/{mw_id} on PATCH is returning misleading response status

[ajoaoff]

Original issue opened by @ArturoQuintana at kytos#44.

• The action to PATCH a payload where the items field is empty is returning 201 when it should be 400.

Example:
payload1 = {
"start": start.strftime(TIME_FMT),
"end": new_time.strftime(TIME_FMT)
}
mw_api_url = KYTOS_API + '/maintenance/' + mw_id
request = requests.patch(mw_api_url, data=json.dumps(payload1), headers={'Content-type': 'application/json'})

Reflected on end-to-end test:
tests/test_e2e_15_maintenance.py::TestE2EMaintenance::test_036_patch_mw_on_switch_should_fail_wrong_payload_items_empty

• The action to PATCH a payload with no items field is returning 201 when it should be 400.

Example:
payload1 = {
"start": start.strftime(TIME_FMT),
"end": new_time.strftime(TIME_FMT)
}
mw_api_url = KYTOS_API + '/maintenance/' + mw_id
request = requests.patch(mw_api_url, data=json.dumps(payload1), headers={'Content-type': 'application/json'})

Reflected on end-to-end test:
tests/test_e2e_15_maintenance.py::TestE2EMaintenance::test_038_patch_mw_on_switch_should_fail_wrong_payload_no_items_field

• A PATCH action using a not serializable JSON broke the application, and it should return a 400 error.

Example:
payload1 = {
"description"
}
mw_api_url = KYTOS_API + '/maintenance/' + mw_id
request = requests.patch(mw_api_url, data=json.dumps(payload1), headers={'Content-type': 'application/json'})

Reflected on end-to-end test: tests/test_e2e_15_maintenance.py::TestE2EMaintenance::test_039_patch_mw_on_switch_should_fail_wrong_payload