feat: Add generic database connection mechanism

[adwk67]

Description

Part of stackabletech/issues#238

🟢 Openshift:

--- PASS: kuttl (827.29s)
    --- PASS: kuttl/harness (0.00s)
        --- PASS: kuttl/harness/logging_superset-6.0.0_openshift-true (130.07s)
        --- PASS: kuttl/harness/oidc_superset-6.0.0_openshift-true (145.06s)
        --- PASS: kuttl/harness/external-access_superset-6.0.0_openshift-true (117.06s)
        --- PASS: kuttl/harness/opa_superset-6.0.0_opa-latest-1.12.3_openshift-true (279.19s)
        --- PASS: kuttl/harness/cluster-operation_superset-latest-6.0.0_openshift-true (171.86s)
        --- PASS: kuttl/harness/druid-connection_superset-6.0.0_openshift-true (108.01s)
        --- PASS: kuttl/harness/smoke_superset-6.0.0_openshift-true (121.00s)
        --- PASS: kuttl/harness/ldap_superset-6.0.0_ldap-authentication-server-verification-tls_openshift-true (123.83s)
        --- PASS: kuttl/harness/ldap_superset-6.0.0_ldap-authentication-insecure-tls_openshift-true (133.56s)
        --- PASS: kuttl/harness/resources_superset-latest-6.0.0_openshift-true (99.16s)
        --- PASS: kuttl/harness/ldap_superset-6.0.0_ldap-authentication-no-tls_openshift-true (128.67s)
PASS

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Helm chart can be installed and deployed operator works
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible
• Links to generated (nightly) docs added
• Release note snippet added

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added
• Links to generated (nightly) docs added
• Release note snippet added
• Add type/deprecation label & add to the deprecation schedule
• Add type/experimental label & add to the experimental features tracker

[sbernauer]

Thanks, this already looks very good!

[adwk67]

Starting another round of tests: 🟢 https://testing.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/superset-operator-it-custom/44/

[sbernauer]

Thanks!