Remove OPA filter dependency.base calculation in optional body parsing

[Pushpalanka]

Due to a detected performance concern for CPU as seen below,

Memory profile

alloc_objects profile

Load test results

Using a request body as below with a simple policy to check email domain.

{
      "email": "loadtest@zalando.de",
      "user": {
        "id": "12345",
        "name": {
          "first_name": "John",
          "last_name": "Doe"},
        "contact": {
          "phone_number": "+49-123-456-7890",
          "address": {
            "street": "Main Street 123",
            "city": "Berlin",
            "zip_code": "10115",
            "country": "Germany"}}},
      "account": {
        "created_at": "2023-08-28T10:15:30Z",
        "status": "active",
        "preferences": {
          "language": "en",
          "currency": "EUR"},
        "subscriptions": {
          "newsletter": true,
          "alerts": {
            "email": true,
            "sms": false}}},
      "meta": {
        "last_login": "2023-08-28T10:20:00Z",
        "login_count": 42,
        "roles": [
          "user",
          "tester"],
        "tags": [
          "load-test",
          "test-user"]}
    }

Before this improvement
23 instances for 1000 rps
max GC pause : 500 µs (high number of small objects generated by the dependency.base functions seems to have contributed here)
max heap objects : 3.17M
max heap usage: 557 MB

After this improvement
11 instances for 1000 rps (50% reduced of CPU power)
max GC pause: 269 µs.
max heap objects : 1.28M (50% reduced.)
max heap usage: 236 MB

Bench-mark test results

Before
BenchmarkAuthorizeRequest/authorize-request-with-body-8 10002 1068249 ns/op 8432573 B/op 806 allocs/op

After
BenchmarkAuthorizeRequest/authorize-request-with-body-8 13461 587883 ns/op 8418624 B/op 566 allocs/op

[szuecs]

@Pushpalanka please also --sign-off the commit (DCO).

[mjungsbluth]

👍

[MustafaSaber]

maybe the image for the CPU profile after would be great also to visualise the difference

[MustafaSaber]

👍

[Pushpalanka]

maybe the image for the CPU profile after would be great also to visualise the difference

Here we go,

memory profile, (at 1000 rps ~32MB for body parsing.)