Add how to create custom domains with kn domain

[rhuss]

Proposed Changes

• Add a description of how to leverage kn domain for managing custom domains
• Extended YAML description for CustomDomain include the tls: section for enabling HTTPS

Note, that I'm not sure about the formatting as I add the kn usage in the middle of a numbered list and am not sure how it will be rendered. Any help for fixing the formatting is appreciated.

Fixes #3496

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[snneji]

Hi @rhuss, some of the formatting fixes will need to span lines that you've not edited in the PR, so it will be difficult for me to use the suggestion feature to suggest the correct formatting.

Would it be OK to merge the PR and then open a cleanup issue for us to fix the formatting and style for you? Or would you prefer me to leave comments on the PR for you to fix the formatting yourself?

[rhuss]

@snneji happy to merge it now and hand it over to you to fix the formatting. So maybe give it a quick look about whether the content is fine so far ?

[snneji]

Looks OK to merge to me. Just a small fix here and the rest of the fixes can be dealt with in the cleanup issue.

One other thing - does this PR need to be cherry picked? It seems to be based on an issue that was first created for v0.22.

[rhuss]

kn supports the domain command since 0.22, not sure about the tls: option though. @julz do you know when tls: was introduced to DomainMapping ? Was it there from the beginning ?

[julz]

wasn't there in the beginning, looks like it landed in 0.24 (same time DM went beta)

[snneji]

/lgtm

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[snneji]

Issue to fix formatting: #4225