normalize whitespace-only CodeMirror input

[skanakal]

Summary

Fixes #16317

Occurred changes and/or fixed issues

validate the input at the CodeMirror component

Technical notes summary

The CodeMirror.vue component’s onInput() handler forwarded editor output directly..
Whitespace-only values were not detected.

Areas or cases that should be tested

Areas which could experience regressions

Screenshot/Video

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[richard-cox]

what do the codemirror docs say, anything in their repo issues about this? if a bug is it in their implementation or our integration?

[richard-cox]

how do we know that users will never need a whitespace value?

[skanakal]

Initially, I assumed Kubernetes treated whitespaces values as empty and added trimming logic based on that assumption but that wasn't for configmap...
It doesn't look like a bug to me, deleting the last character often leaves a "ghost space" in the editor buffer...our CSS renders a "dot" for every space, that ghost space creates a visual bug...

• doc.getValue() to get the content and doc.setValue(content: string) to set it to empty which strips the .cm-markdown-single-trailing-space class from the DOM, which causes the "dot" to disappear...

[richard-cox]

The question revolved around this being a generic component to display text where a blank space might be expected or required. So i think we can move away from kube specific requirements.

Something is adding that white space when it shouldn't do, feels like the solution should be to address that part rather than working around it.