utf8-url encoded username url support (simple solve)

[shangjiaxuan]

Feature Request

Is your feature request related to a problem? Please describe.
I am having problem if I manually allow usernames to contain spaces and non-ASCII characters and use a link to go to the user page, it would trigger a 404 error (url encoded strings are not converted).

Describe the solution you'd like
A detailed description of your proposed solution. Include:

• How the feature would work/behave
• Any potential drawbacks
• Maybe a screenshot, design, or example code

Modify the following kines in function protected function data(ServerRequestInterface $request, Document $document) in src/Api//Controller/ShowUserController.php

if (! is_numeric($id)) {
    $id = $this->users->getIdForUsername($id);
}

to

if (! is_numeric($id)) {
    $id = $this->users->getIdForUsername(urldecode($id));
}

Tested on my forum at this site. As shown here in Firefox:

Justify why this feature belongs in Flarum's core, rather than in a third-party extension
This changes the behavior of core api. Also the overhead involved with a decode on strings that are not percent-encoded may not be too high (not metered). This would allow removing the restriction on username characters (spaces allowed as encoded %20 in url request) at least on the user display side.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.
Probably implement this somewhere in a extension.

[shangjiaxuan]

grep -r 'numeric' on src directory gives only this and a line in ./Util/Str.php, and grep -r 'alpha' only gives ./Util/Str.php. Most likely there won't be security issues involved.

[shangjiaxuan]

Note: Using space in username breaks post cross referencing. Allowing space is more tricky here.

[shangjiaxuan]

It seems that this post mentions a rather good solution to the username with @mention system by recognizing @"mention user". Making this and changing a bit how UserValidater.php works (allow more characters) should allow an complete extension that allow spaces, non-ascii and other characters in the username.

[luceos]

related #1356

[franzliedke]

More cross-reference: #557 and flarum/issue-archive#254

[tankerkiller125]

I'm not a huge fan of allowing space, but I did discover that apha_dash as the validator instead of regex would allow unicode characters to be used as a username. We would need to figure out proper slugging though.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. We do this to keep the amount of open issues to a manageable minimum.
In any case, thanks for taking an interest in this software and contributing by opening the issue in the first place!

[stale]

We are closing this issue as it seems to have grown stale. If you still encounter this problem with the latest version, feel free to re-open it.