Add unknown field check to beta validate

[enesonus]

Description of your changes

This PR implements a validation logic that use pruning to get the unknown fields of a resource. With the help of this new validation step we can get informed about the typos and indentation errors.

Here are some examples of this new validation:

1. XR validation:

xrd.yaml
xr.yaml:

apiVersion: example.crossplane.io/v1beta1
kind: UserAccess
metadata:
  name: example
spec:
  count: 2
  accesKey: true  # an unknown field

Output:

go run cmd/crank/main.go beta validate ./.work/xfn/ ./.work/xfn/xr.yaml
[x] schema validation error example.crossplane.io/v1beta1, Kind=UserAccess, example : spec.accesKey: Invalid value: "accesKey": unknown field: "accesKey"
Total 1 resources: 0 missing schemas, 0 success cases, 1 failure cases
crossplane: error: cannot validate resources: could not validate all resources
exit status 1

2. Piping crossplane beta render function with field errors at composition:

Uses jbw976/demo-upbound@38017fa which has a typo, indentation error and unknown field

crossplane beta render .work/xfn/xr.yaml  .work/xfn/composition.yaml  .work/xfn/functions.yaml --include-full-xr | go run cmd/crank/main.go beta validate .work/xfn/ - 
package schemas does not exist, downloading:  xpkg.upbound.io/upbound/provider-aws-iam:v1.6.0
[x] schema validation error example.crossplane.io/v1beta1, Kind=UserAccess, example : spec.accesKey: Invalid value: "accesKey": unknown field: "accesKey"
[x] schema validation error iam.aws.upbound.io/v1beta1, Kind=AccessKey, sample-access-key-0 : spec.forProvider.userSelectorFoo: Invalid value: "userSelectorFoo": unknown field: "userSelectorFoo"
[x] schema validation error iam.aws.upbound.io/v1beta1, Kind=AccessKey, sample-access-key-0 : spec.pgpKey: Invalid value: "pgpKey": unknown field: "pgpKey"
[x] schema validation error iam.aws.upbound.io/v1beta1, Kind=AccessKey, sample-access-key-0 : spec.writeConnectionSecretToRef.fookey: Invalid value: "fookey": unknown field: "fookey"
[x] schema validation error iam.aws.upbound.io/v1beta1, Kind=AccessKey, sample-access-key-1 : spec.forProvider.userSelectorFoo: Invalid value: "userSelectorFoo": unknown field: "userSelectorFoo"
[x] schema validation error iam.aws.upbound.io/v1beta1, Kind=AccessKey, sample-access-key-1 : spec.pgpKey: Invalid value: "pgpKey": unknown field: "pgpKey"
[x] schema validation error iam.aws.upbound.io/v1beta1, Kind=AccessKey, sample-access-key-1 : spec.writeConnectionSecretToRef.fookey: Invalid value: "fookey": unknown field: "fookey"
[✓] iam.aws.upbound.io/v1beta1, Kind=User, test-user-0 validated successfully
[✓] iam.aws.upbound.io/v1beta1, Kind=User, test-user-1 validated successfully
Total 5 resources: 0 missing schemas, 2 success cases, 3 failure cases
crossplane: error: cannot validate resources: could not validate all resources
exit status 1

Fixes: #5376

I added the relevant changes made in this PR to docs: crossplane/docs#790

I have:

• Read and followed Crossplane's contribution process.
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• Added or updated unit tests.
• Added or updated e2e tests.
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[jbw976]

Super cool @enesonus to see the validate functionality getting extended with more useful checks - great start to your LFX mentorship summer 💪

All the validation looks to be working correctly, I've added just a few comments for you to consider 🙇‍♂️

[jbw976]

OK @enesonus, I responded to the comments here, so please go ahead and update the code to use the invalid error type, and then add some unit tests (e.g. new test cases in validate_test.go) 🙇‍♂️

[ezgidemirel]

@enesonus thanks for the PR! This is the most requested/asked functionality for the validate command. Do you mind updating the example in the PR description with your latest changes (e.g., Internal error vs Invalid)?

[enesonus]

@enesonus thanks for the PR! This is the most requested/asked functionality for the validate command. Do you mind updating the example in the PR description with your latest changes (e.g., Internal error vs Invalid)?

Thanks for the reminder! I updated it to the latest error string now.

[jbw976]

This functionality looks great now, let's get it merged in so it can ship in v1.17! 🎉