Adding http handler for lookup subjects stream response

[akoserwal]

PR Template:

Add HTTP handler for Lookup subjects

Describe your changes

As Kratos doesn't support stream for HTTP

I implement an HTTP handler for the Subject Lookup endpoint. I follow the same approach as the grpc-gateway project to convert gRPC to HTTP.

Request

curl --location --request GET 'http://localhost:8000/api/authz/v0/subjects' \
--header 'Content-Type: application/json' \
--data '{
    "subject_type": {
        "name": "group"
    },
    "subject_relation": "member",
    "relation": "member",
    "resource": {
        "type": {
            "name": "group"
        },
        "id": "omni"
    }
}' 

Response

[
    {
        "subject": {
            "subject": {
                "type": {
                    "name": "group"
                },
                "id": "omni"
            }
        },
        "pagination": {}
    }
]

Ticket reference (if applicable)

Fixes #

Checklist

• Are the agreed upon acceptance criteria fulfilled?

• Was the 4-eye-principle applied? (async PR review, pairing, ensembling)

• Do your changes have passing automated tests and sufficient observability?

• Are the work steps you introduced repeatable by others, either through automation or documentation?

  • If automation is possible but not done due to other constraints, a ticket to the tech debt sprint is added
  • An SOP (Standard Operating Procedure) was created

• The Changes were automatically built, tested, and - if needed, behind a feature flag - deployed to our production environment. (Please check this when the new deployment is done and you could verify it.)

• Are the agreed upon coding/architectural practices applied?

• Are security needs fullfilled? (e.g. no internal URL)

• Is the corresponding Ticket in the right state? (should be on "review" now, put to done when this change made it to production)

• For changes to the public API / code dependencies: Was the whole team (or a sufficient amount of ppl) able to review?

[app-sre-bot]

Can one of the admins verify this patch?

[Rajagopalan-Ranganathan]

Is it possible to add some unit tests for this? WDYT?

[Rajagopalan-Ranganathan]

decision: will not add streaming response support in http for now, will revisit it later when required