Make splitting while pasting multiline instructions configurable

Recently this message was posted in another issue:

Hi @christianlupus I hope you don't mind if I add a comment here, since it is somehow related (newlines).

I'm also a new user and created my first recipe today. I stumbled over the creation process for the instructions, where any newline creates a new instruction step. When you really create all the instructions in that moment this is very helpful. You can create multiline steps with Shift+Enter and a new step with Enter.

But I wanted to copy paste a multiline text in one instruction step, which is not possible, because any newline in the clipboard also creates new steps. For me it would be really great if only a manually pressed Enter key would create a new step and not newlines from the clipboard.
I could also imagine having a special character (e.g. <br> or something) which is interpreted as "inside instruction step" newline but not "create a new step" newline.

If this is even possible?

Led me add, that having less instruction steps, also saves space in the printed version of a recipe.

Originally posted by @efelon in https://github.com/nextcloud/cookbook/issues/1231#issuecomment-1326711751

As this issue was unrelated to the topic it was posted in, it should be tracked in a new issue (here).

Related subtopics:

• Find consent on what is the best UI/UX solution to allow for pasting
• Enable merging of adjacent instructions while editing

Depends on #1067

Start by reviewing the dependency in #1067 and the related discussion linked from the issue. Agree on the UI/UX for pasted newlines, then implement configurable splitting and merging of adjacent instruction steps while editing. Done means the chosen paste behavior works without disrupting manually created steps.