fix(core): fix insertContentAt keeping new lines in html content

[bdbch]

Please describe your changes

This PR fixes the issue described in #2720 which was caused by keeping new lines in string content and using the DOMParser which will add breaks for new lines too.

How did you accomplish your changes

I strip out \n content from the content string so new lines are interpretet by the DOMParser only.

How have you tested your changes

I created a demo where this can be tested. (See here)

How can we verify your changes

Test in the demo above

Checklist

• The changes are not breaking the editor
• Added tests where possible
• Followed the guidelines
• Fixed linting issues

Related issues

• fixes The insertContent command adds unnecessary blank paragraphs with HTML as value #2720

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[bdbch]

@svenadlung can you take a look too? self reviewing right now.

[bdbch]

Update: Found some more issues I'd have to take a look into.

[bdbch]

Okay - ready. @svenadlung if you have some time a review would be great.

[bdbch]

Ping @svenadlung

[svenadlung]

@bdbch Sorry for the delay. At the first moment it feels to me like something could break of the change. Please give me some more time for a review. Probably until the end of next week due to public holidays.

[gdfreitas]

We're also facing this issue, do we have any updates? @svenadlung

[kaiserkiwi]

Any progress here?

[bdbch]

@svenadlung should we include this in our next release or should we postpone it for a later release?

[murisceman]

This fix breaks <pre><code>foo\nbar</code></pre>.

[bdbch]

working on a fix @murisceman

[bdbch]

PR is here: #4767