Bug: ensure src of iframe for a ref stays the same, unless the version changes

[ndelangen]

Closes #21499

What I did

I ensured that when rendering iframes we don't change the src attribute of the iframe unless the base-url changes (the version changed)

How to test

1. Add a ref
2. Start and load storybook
3. Go to the composed storybook
4. Switch between stories

Expect no loaders/spinner and no refreshes

[ndelangen]

Thank you for the critical eye @tmeasday
It's super appreciated!

I took another look at the code, tried to work out what the intention really is, and was able to simplify a lot, i think.

Care to take another look?
I verified this works on my machine

I even suspect this will be a little more performant too.

[tmeasday]

I like this as it is more consistent with what we do for the main frame (set it once when we first boot and then never again).

However I'm wondering about losing this logic:

If I understand the old code directly, it's saying we need to add iframes for auto-inject refs even before they are selected. Is this the type of ref where we don't have an index.json (ie SSv6) so we need to wait for the SET_STORIES (now SET_INDEX) event in order to render the sidebar?

If so, we'll have a chicken and egg situation if we don't show the frame before the ref is selected (it won't be possible to select the ref because we haven't rendered it yet).

[ndelangen]

Ah yes, you're right, the auto-inject refs should be part of the initial state, I'll add it!

[tmeasday]

Yes! I love it @ndelangen -- much cleaner now.