Support for HeadingLevel in collapsible sections

[shunsaker]

Support for HeadingLevel in collapsible sections
See #1686

[jansenbe]

@shunsaker : nice work!

Question: if the default is 2, I think it's also needed to ensure HeadingLevel value is initialized to 2. We cannot assume every page has this value in it's json payload + we need to support creating pages where developers don't set the heading level

[shunsaker]

@shunsaker : nice work!

Question: if the default is 2, I think it's also needed to ensure HeadingLevel value is initialized to 2. We cannot assume every page has this value in it's json payload + we need to support creating pages where developers don't set the heading level

@jansenbe
I thought about that. When it is empty sharepoint makes it 2, so it seemed okay to leave it empty and tell Json not to serialize it if it is 0. Which is exactly what it does today because it can't set that property

[jansenbe]

Thx @shunsaker : I'll do some testing with the PR

[shunsaker]

@jansenbe Bump. Have a minor feature blocked by this