The feature authentication affords recovery from CONFERENCE_FAILED
caused by AUTHENTICATION_REQUIRED. (Like the feature room-lock afforded
recovery from CONFERENCE_FAILED caused by PASSWORD_REQUIRED.)
* Javadoc introduced @code as a replacement of <code> and <tt> which is
better aligned with other javadoc tags such as @link. Use it in the
Java source code. If we switch to Kotlin, then we'll definitely use
Markdown.
* There are more uses of @code in the JavaScript source code than <tt>
so use @code for the sake of consistency. Eventually, I'd rather we
switch to Markdown because it's easier on my eyes.
* Xcode is plain confused by @code and @link. The Internet says that
Xcode supports the backquote character to denote the beginning and end
of a string of characters which should be formatted for display as
code but it doesn't work for me. <tt> is not rendered at all. So use
the backquote which is rendered itself. Hopefully, if we switch to
Markdown, then it'll be common between JavaScript and Objective-C
source code.
Gradually, we exploded the error of CONNECTION_FAILED in multiple
redux state properties. The explosion makes maintenance harder because
the properties have to be updated in sync. Collect them in an object
resembling an Error instance.