docs: mounting volumes, secrets and configmaps for devworkspaces

[dkwon17]

Signed-off-by: David Kwon dakwon@redhat.com

What does this pull request change

• Replaces the current mounting docs for devworkspace-specific mounting docs.
• Adds Creating image pull Secrets section

Before this PR:

After this PR:

Sources used:

• https://github.com/devfile/devworkspace-operator/blob/v0.14.1/docs/additional-configuration.md
• https://docs.openshift.com/container-platform/4.7/openshift_images/managing_images/using-image-pull-secrets.html#images-allow-pods-to-reference-images-from-secure-registries_using-image-pull-secrets
  do
• https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/

What issues does this pull request fix or reference

eclipse-che/che#21299

Specify the version of the product this pull request applies to

Pull request checklist

The author and the reviewers validate the content of this pull request with the following checklist, in addition to the automated tests.

• Any procedure:
  • Successfully tested.
• Any page or link rename:
  • The page contains a redirection for the previous URL.
  • Propagate the URL change in:
    • Dashboard default branding data
    • Chectl constants.ts
• Builds on Eclipse Che hosted by Red Hat.
• the Validate language on files added or modified step reports no vale warnings.

[github-actions]

Click here to review and test in web IDE:

[max-cx]

I will review this PR.

[dkwon17]

Thank you @max-cx, I've edited the PR description to provide some context

[l0rd]

Instead of having one main section "mounting volumes, secrets and configmaps" I would split like this:

1. Injecting configurations and credentials (that's about CM, Secrets)
   a. Configuring git
   b. Configuring container registries
2. Persisting and sharing files (that's about pre created PVs)

[dkwon17]

Thanks a lot for the reviews @max-cx , @l0rd. I've applied and made new changes.

[dkwon17]

Preview of the main section:

[max-cx]

@dkwon17, my next PR is ready dkwon17#11

[dkwon17]

I don't think the current build failure is caused by this PR. I get the same failure in the master branch:

========================================================================
docs/next/administration-guide/checluster-custom-resource-fields-reference/index.html
  Non-OK status: 404 --- docs/next/administration-guide/checluster-custom-resource-fields-reference/index.html --> https://developers.redhat.com/products/openshift-dev-spaces/overview
docs/next/administration-guide/supported-platforms/index.html
  Get "https://developers.redhat.com/products/codeready-containers/overview": stopped after 10 redirects --- docs/next/administration-guide/supported-platforms/index.html --> https://developers.redhat.com/products/codeready-containers/overview
========================================================================
✘✘✘ failed in 1.377997186s
2 errors in 357 documents

[max-cx]

@dkwon17, pls see more edits from me in the form of dkwon17#13.

[max-cx]

LGTM