This commit introduces the ability to edit the channel
slug from the About tab for the chat channel when the user
is admin. Similar to the create channel modal functionality
introduced in 641e94f, if
the slug is left empty then we autogenerate a slug based
on the channel name, and if the user just changes the slug
manually we use that instead.
We do not do any link remapping or anything else of the
sort, when the category slug is changed that does not happen
either.
This commit allows us to set the channel slug when creating new chat
channels. As well as this, it introduces a new `SlugsController` which can
generate a slug using `Slug.for` and a name string for input. We call this
after the user finishes typing the channel name (debounced) and fill in
the autogenerated slug in the background, and update the slug input
placeholder.
This autogenerated slug is used by default, but if the user writes anything
else in the input it will be used instead.
