Fixes https://github.com/vector-im/element-web/issues/18786
Instead of replacing the remembered set, we now add to it. This should be safe as the user expectation was previously to remember the capabilities, so we can keep appending to that list.
This commit also moves the utility functions closer to the widget driver as they aren't needed in the dialog anymore.
Fixes https://github.com/vector-im/element-web/issues/18035 (indirectly; issue is on a non-standard version of Element).
This has an isReady() step because the variable usage code path cannot be made async, so instead we let the async loading state happen in the prepare() stage. This is required for the intended usecase.
If your homeserver is configured with an experiment `widget_build_url`, this
will take over the functionality of the call buttons and turn them into a
general widget installer.
Note that this ditches all previously set width values, however this is probably acceptable for now. Trying to remain backwards compatible gets tricky on top of already tricky code, and the impact of Element forgetting widths is not as severe as forgetting which widgets were/are pinned.
The security key naming/practice was misguided, so let's call it what it is (a settings key) and abstract away the complexity to a new store.
Fixes https://github.com/vector-im/element-web/issues/15820 while we're here.
The "remember my selection" option wasn't working because the `missing` set still included the approved permission. Solution: remove it from `missing`.
The customisation point is to allow forks to change which widgets get which additional capabilities dependent on their own rules.
Following https://github.com/matrix-org/matrix-react-sdk/pull/5385, it is now possible for a widget to request these capabilities without being a video conference or sticker picker. This commit actually enables this support for those kinds of widgets.
This commit also fixes an issue in the URL templating where some variables might get set to 'undefined' - this appears to be a scoping issue, so StopGapWidget now stores the definition alongside the superclass.
Fixes https://github.com/vector-im/element-web/issues/15001
