TI API: error codes update

[FabrizioMoggio]

Problem description
the CAMARA Guidelines specify:
The Following Error codes must be present:

for POST: 400, 401, 403, 409, 415, 429, 500, 503
for GET: 400, 401, 403, 500, 503
for GET .../{subscriptionId}: 400, 401, 403, 404, 500, 503
for DELETE: 400, 401, 403, 404, 500, 503

In the TI API are missing:

for POST: 409, 415, 429
for GET: 400
for GET .../{subscriptionId}: 400
for DELETE: 400, 500,

Expected behavior
introduce the missing error codes

The error code template is here: https://github.com/camaraproject/Commonalities/blob/main/artifacts/CAMARA_common.yaml

[FabrizioMoggio]

Fixed with: #315