Validate private network for cloudsql is in expected format

[turkenh]

Description of your changes

Google Cloud API expects the resource link for the VPC network for the CloudSQL private network field. However, it also accepts VPC name (e.g. "default") but looks like it internally converts it to resource link by assuming it is in the same project, (projects/[project]/global/networks/[name]). This is causing issues like #352 where users are not aware about the underlying problem.

This PR adds a pattern validation on CRD using kubebuilder marker (thanks @hasheddan for pointing that out).

Fixes #352

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

1. Create a cloudsql instance in the expected format and verify it is created properly (and not getting periodic updates)
2. Create the following resource and verify that a proper error is reported:

apiVersion: database.gcp.crossplane.io/v1beta1
kind: CloudSQLInstance
metadata:
  name: sre-6-db-hasan-bug352-4
  namespace: crossplane
spec:
  deletionPolicy: "Orphan"
  forProvider:
    databaseVersion: POSTGRES_11
    region: europe-west1
    settings:
      ipConfiguration:
        ipv4Enabled: false
        privateNetwork: default
      tier: db-custom-1-3840
  writeConnectionSecretToRef:
    name: db-connection
    namespace: default

$ kubectl create -f cloudsql.yaml

The CloudSQLInstance "cloudsql-bug352" is invalid: spec.forProvider.settings.ipConfiguration.privateNetwork: Invalid value: "default": spec.forProvider.settings.ipConfiguration.privateNetwork in body should match '^projects\/.+'

[turkenh]

This is indeed the same comment as the one gcloud API: https://cloud.google.com/sql/docs/mysql/admin-api/rest/v1beta4/instances#IpConfiguration

However, using this format (with leading /) does not work actually:

create failed: cannot create new CloudSQL instance: googleapi: Error 400: Invalid request: Project redacted-project has invalid private network name /projects/redacted-project/global/networks/default., invalid

[hasheddan]

Looks like this may have been copied over from tags initializer

[turkenh]

Fixed 👍

[hasheddan]

@turkenh would it be possible to use the CRD field Pattern validation for this? https://book.kubebuilder.io/reference/markers/crd-validation.html

[turkenh]

@turkenh would it be possible to use the CRD field Pattern validation for this? https://book.kubebuilder.io/reference/markers/crd-validation.html

Definitely, Thanks for pointing out!
Updated the PR.

[hasheddan]

Nice! Thanks @turkenh :)