api: adds CRUD operations for policy labels

[ashwiniag]

closes #52

Introduces

• CRUD operations
• OpenAPI spec
• logic dependent on policies + policylabels
• adds test cases api: add tests for policy labels #53

As follows

Action	Method	Endpoint	Description
Create	POST	/policies/{policy_id}/labels	Add a new label to a policy.
Read (List)	GET	/policies/{policy_id}/labels	List all labels for a specific policy.
Read (Multiple keys)	GET	/policies/{policy_id}/labels?key={key1}&key={key2}	Returns labels matching the provided keys for the specified policy_id
Read (Detail)	GET	/policies/{policy_id}/labels/{key}	Returns labels matching the provided single key for the specified policy_id
Update	PUT	/policies/{policy_id}/labels/{key}	Update a specific label by key.
Delete	DELETE	/policies/{policy_id}/labels/{key}	Delete a specific label by key.

cURL

curl -X POST \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
-d '{
  "key": "newkey",
  "value": "new_value"
}' \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels

curl -X GET \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels


curl -X GET \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels?key=env&key=lts_version

curl -X GET \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels/lts_version

curl -X PUT \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
-d '{
  "key": "newkey",
  "value": "updated_value"
}' \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels

curl -X PUT \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
-d '{
  "labels": [
    {"key": "lts_version", "value": "v1.0"},
    {"key": "team", "value": "gokakashi"}
  ]
}' \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels

curl -X DELETE \
-H "Authorization: Bearer letsdoit" \
-H "Content-Type: application/json" \
-d '{
  "value": "v1.0"
}' \
http://localhost:8000/api/v1/policies/2fe7c0e8-e042-4e35-bb7f-1b0c20f40d59/labels/lts_version

POST /policies/{policy_id}/labels

Test Case	Description	Error Handling
Valid Input	Ensure a new label is created successfully for a policy. ✅	Response contains key and value of the created label. ✅
Missing Required Fields	Verify error when policy_id, key, or value is not provided. ✅	Returns 400 Bad Request. ✅
Duplicate Key for Same Policy ID	Verify error when the same key already exists for the policy ID. ✅	Returns 409 Conflict. ✅

GET

Test Case	Description	Error Handling
List Valid Policy Labels	Retrieve all labels for a policy ID. ✅	Returns a list of all labels with key and value. ✅
No Labels Found	Verify behavior when no labels are associated with the policy ID. ✅	Returns an empty list. ✅
Get Specific Label	Fetch a specific label by key for a policy ID. ✅	Response contains the key and value. ✅
Non-Existent Label or Policy ID	Verify error when attempting to fetch a non-existent label or policy ID. ✅	Returns 404 Not Found. ✅

PUT

Test Case	Description	Error Handling
Update a Single Label	Update a specific label's value for a given policy ID. ✅	Response contains the updated key and value. ✅
Replace All Labels	Replace all labels for a policy ID with a new set of labels. ✅	Deletes existing labels, inserts new ones, and ensures success response. ✅
Invalid Input for Update	Verify error when invalid policy ID, key, or value is provided.	Returns 400 Bad Request. ✅

DELETE

Test Case	Description	Error Handling
Delete Existing Label	Delete an existing label by key and value. ✅	Response indicates successful deletion. ✅
Delete Non-Existent Label	Verify error when attempting to delete a non-existent label or policy ID. ✅	Returns 404 Not Found. ✅
Invalid Input for Delete	Verify error when policy ID, key, or value is invalid or empty. 🔺 To be done later	Returns 400 Bad Request. ✅