compose: Show the Refresh/Subscribe banner when can send, too

[chrisbobbe]

Fixes #1798.

Notable commit message:

compose: Show the Refresh/Subscribe banner when can send, too

Fixes #1798.

In #1873, we started showing a Refresh/Subscribe banner when viewing
an unsubscribed channel -- but only if you didn't have permission to
send messages there. We postponed showing it in the case where you
*can* send messages because the UI message for that case is "Replies
to your messages will not appear automatically", and that message
would have been confusing in a world where your own messages didn't
appear automatically either because of bugs that hadn't been fixed.

We've fixed those bugs in #2034 -- the "first" and "third" parts
of #1798 -- so now go ahead and offer the Refresh/Subscribe banner,
with the planned text, in the case where you can send messages.

This completes the work for #1798.

Also a few other behavior changes:

• The label and buttons of the "Refresh/Subscribe" banner that we already show (when you can't send messages) are now a bit more compact. The new banner uses the same compact layout, because it also has long text, but other banners are unaffected.
• When you're viewing a channel that doesn't actually exist, the banner says "You cannot send messages here." instead of "You do not have permission to post in this channel.", which was implying that the channel does exist.
• We stop offering a compose box when you don't have content access to a channel. Alya's suggestion: msglist: Friendlier placeholder text when narrow has no messages #1947 (comment)
• We stop offering a compose box when DM recipients are unknown users. Alya's suggestion: msglist: Friendlier placeholder text when narrow has no messages #1947 (comment)

Screenshots coming up.

[chrisbobbe]

cc @alya

Main feature implemented:

Before	After

Other behavior changes described above:

Before	After

Several of those screenshots are a reminder that we just show an infinite loading spinner if we fail to fetch the first batch of messages. I didn't find an issue for that, so I've just filed #2085.

[rajveermalviya]

Thanks @chrisbobbe! All LGTM and tests great. Couple of comments below about lingering l10n entries, I am not sure if Weblate automatically garbage collects them.

Moving over to Greg's review.

[rajveermalviya]

commit 7f397e42a413544a6830ea5c7f567630223a0fac 

compose [nfc]: Rename a localizations string for its intended use
…

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I think you'll also need to manually remove errorBannerCannotPostInChannelLabel and @errorBannerCannotPostInChannelLabel entries from other assets/l10n/app_*.arb files. Not sure if there is better way to do this.

[gnprice]

Better yet, rename those entries. That way Weblate will pick up the existing values, and won't ask translators to re-translate the strings.

I'd do that with a find-and-replace: from the command line, something like perl -i -pe 's/errorBannerCannotPostInChannelLabel/composeBoxBannerLabelCannotSendInChannel/g' assets/l10n/*.arb, but if one has a favorite other find-and-replace tool then that should work fine too.

[rajveermalviya]

commit 92cff0af1cc87fd91e3f9dffc5d35d1910f4a734

compose [nfc]: Name/describe a localization string more like its friends

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Same here for errorBannerDeactivatedDmLabel and @errorBannerDeactivatedDmLabel.

[gnprice]

Thanks @chrisbobbe for taking care of this, and @rajveermalviya for the previous review!

The code all LGTM except the points Rajesh mentioned above. If @alya has product feedback, we can also incorporate that, though this situation in the app isn't a critical one so it's possible she won't get to it soon.