usersession/userd: add zoommtg url support

[anonymouse64]

Originally committed by @troyready in #8254

[zyga]

+1

[codecov-io]

Codecov Report

Merging #8304 into master will increase coverage by 0.00%.
The diff coverage is 81.32%.

@@           Coverage Diff            @@
##           master    #8304    +/-   ##
========================================
  Coverage   80.65%   80.65%            
========================================
  Files         717      724     +7     
  Lines       57254    57632   +378     
========================================
+ Hits        46177    46484   +307     
- Misses       7481     7513    +32     
- Partials     3596     3635    +39     

Impacted Files	Coverage Δ
bootloader/bootloader.go	68.51% <ø> (ø)
cmd/snap-bootstrap/bootstrap/bootstrap.go	49.38% <0.00%> (-1.26%)	⬇️
cmd/snap-bootstrap/main.go	40.74% <0.00%> (-1.57%)	⬇️
cmd/snap-repair/cmd_run.go	55.81% <0.00%> (ø)
daemon/api_recovery.go	0.00% <0.00%> (ø)
image/helpers.go	67.01% <0.00%> (ø)
interfaces/builtin/greengrass_support.go	100.00% <ø> (ø)
interfaces/builtin/openvswitch_support.go	100.00% <ø> (ø)
interfaces/builtin/udisks2.go	100.00% <ø> (ø)
overlord/patch/patch5.go	6.45% <0.00%> (ø)
... and 86 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a4112a7...7f678b9. Read the comment docs.

[mvo5]

What's the status here, do we need jamie or can this go in as is?

[anonymouse64]

@mvo5 waiting on @jdstrand since Jamie didn't approve the original one

[jdstrand]

I asked in #8254 (comment) about the contents of the URL, but didn't get back anything definitive, so I looked and found: https://medium.com/zoom-developer-blog/zoom-url-schemes-748b95fd9205. The contents of the URL scheme are fine and this PR can be applied as is.

That said, should we also include "zoomus"? Based on the above blog, it seems 'no', but I'm not familiar with zoom URL schemes so I'm not sure. That shouldn't block this PR since if it comes up we can add it later.

[jdstrand]

This seemed blocked on me so since I provided my review, I removed the blocked tag.

[anonymouse64]

That said, should we also include "zoomus"?

@jdstrand let's say no until someone asks us for it. I haven't seen it in the wild either

[nermolov]

Why is this the only custom url scheme allowed through, while there are many many other custom url schemes that are still being blocked?

[troyready]

@nermolov there's a broad fix in a testing release now that should finally address the core URL problem (instead of the previous strategy of whitelisting them).

(I hesitated to comment here on a closed PR & pollute it with comment spam, but since this is a particularly important issue I think it's relevant to cross-post)