Adds support for DefaultPrivileges in postgres

[xocasdashdash]

Description of your changes

Adds support to DefaultPrivileges for postgres.
Fixes #117

I have:

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

How has this code been tested

I've been trying to test this locally but i'm really struggling to deploy the provider to a local kind cluster
It's following the same pattern as the grants, we only care about the creation of the default privileges as the grant/revoke runs in a single transaction.

From xocasdashdash#1 by @fernandezcuesta

Locally with a kind cluster, running from the examples folder and verified with:

  SELECT                                                                                                                                                                                                                                 
      pg_get_userbyid(d.defaclrole) AS target_role,                                                                                                                                                                                        
      CASE d.defaclobjtype                                                                                                                                                                                                                 
          WHEN 'r' THEN 'table'                                                                                                                                                                                                            
          WHEN 'f' THEN 'function'                                                                                                                                                                                                         
          WHEN 'S' THEN 'sequence'                                                                                                                                                                                                         
          WHEN 'T' THEN 'type'
          WHEN 'n' THEN 'schema'
      END AS object_type,
      n.nspname AS schema,
      pg_get_userbyid((aclexplode(d.defaclacl)).grantee) AS grantee,
      (aclexplode(d.defaclacl)).privilege_type
  FROM pg_default_acl d
  LEFT JOIN pg_namespace n ON d.defaclnamespace = n.oid
  ORDER BY target_role, object_type, grantee;

[xocasdashdash]

Well i manage to get this deployed to kind but it involves

• run a registry as a service inside the kind cluster
• running make build
• using crane to export the package as a docker image:

crane push _output/xpkg/linux_arm64/provider-sql-v0.9.0-19.g4d629ee.dirty.xpkg 0.0.0.0:5001/provider-sql-v0.9.0-19.g4d629ee:latest --insecure

• pull the image locally:

docker pull 0.0.0.0:5001/provider-sql-v0.9.0-19.g4d629ee:latest

• retag it matching the crane package:

docker tag 0.0.0.0:5001/provider-sql-v0.9.0-19.g4d629ee:latest registry.crossplane-system.svc.cluster.local:5001/provider-sql-v0.9.0-19.g4d629ee:latest

• Load it with kind into the cluster:

kind --name local load docker-image registry.crossplane-system.svc.cluster.local:5001/provider-sql-v0.9.0-19.g4d629ee:latest

and then it "just works"

[ChrisJBurns]

Would really love this to be merged as we also need to alter default privs

[benjaminlefevre]

Hi, will be the PR one day merged? I also need default privileges.

[xocasdashdash]

Hi, will be the PR one day merged? I also need default privileges.

I've started looking into this PR, there's been several changes in the apis used and I'm trying to get a fix in place but will take some time

[Duologic]

I've scanned through the code, didn't see anything obviously wrong. I don't know too much about Postgres/DefaultPrivileges myself to deeply verify that this is correct. I'm happy to merge it when CI is green.