TT-10640 add support for pdb resource for gateway component

[rakkhin]

Description

As described in #140 having built-in support for PodDisruptionBudget resource will reduce the amount of post-deployment work need to achieve fully highly-available solution.

Testing procedure for the changes:

1. Deploy single node minikube cluster
2. Deploy postgresql and redis (I found issues when deploying redis on non-control plane nodes)
3. Add a second node to the cluster and label it with service=tyk-gateway
4. Deploy Tyk Gateway with appropriate node selector, gateway.replicaCount set to 2, gateway.pdb.enabled set to true and gateway.pdb.minAvailable or gateway.pdb.maxUnavailable set to 1
5. Add a third node to minikube cluster and label it with service=tyk-gateway
6. Drain the second node and observe as Tyk Gateway pods are drained and rescheduled to the third node, one a time
7. Un-cordon second cluster node
8. Delete PodDisruptionBudget deployed by Tyk Gateway chart
9. Drain the third node and observe as Tyk Gateway pods are drained and rescheduled to the second node, all at once

Related Issue

#140

Motivation and Context

It eliminates the need for manual creation of PDB resources in environments with high requirements for HA.

Test Coverage For This Change

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactoring or add test (improvements in base code or adds test coverage to functionality)
• Documentation updates or improvements.

Checklist

• Make sure you are requesting to pull a topic/feature/bugfix branch (right side). If PRing from your fork, don't come from your master!
• Make sure you are making a pull request against our master branch (left side). Also, it would be best if you started your change off our latest master.
• My change requires a change to the documentation.
  • I have manually updated the README(s)/documentation accordingly.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[komalsukhani]

@rakkhin PR looks great. Thank you!
One last question: Have you tested this PR? If so, can you just add details how you tested it in the PR description?

[rakkhin]

@komalsukhani I've updated the description with testing procedure.

[komalsukhani]

@rakkhin Thank you so much!
I will add this PR to our backlog. I'll let you know when it is scheduled for release.

Also, we don't merge the PR unless QA tests it. So once PR is scheduled for release and tested by our QA we will merge it.

[caroltyk]

Hi @rakkhin , thank you for the updates. This PR is scheduled for testing and release in v1.3.0 (tentatively at Jan 2024)

[komalsukhani]

@rakkhin Sorry for delay.
We have tested your PR. It works. Can you resolve the merge conflicts so we can merge?

Also, we have renamed tyk-mdcb-data-plane to tyk-data-plane. So you need to update values of tyk-data-plane instead.

[komalsukhani]

Can you also update values of tyk-control-plane chart?

[komalsukhani]

@rakkhin I created new PR #230 to resolve merge conflicts. Closing this PR in favour of it.
Your change will be available in the upcoming release. Thank you for your contribution.