Add support for Chimera to Zoom plugin

[Szymongib]

Summary

Chimera Proxy is an easier way to connect plugins to external OAuth providers. It provides pre-registered OAuth applications allowing users to skip the app registration step.

Design doc: https://docs.google.com/document/d/1a1AzNwxrqA5bcVonZOVu94b4vV6tT4U7fDIKBwf_aUI/edit

This PR makes it possible to connect Zoom Plugin via Chimera. It introduces:

• New config option, whether to use pre-registered application (Chimera)
• Changes validation if connection through Chimera is enabled
• Creates different OAuth config when using Chimera

Ticket Link

https://mattermost.atlassian.net/browse/MM-37756

[codecov[bot]]

Codecov Report

Base: 0.00% // Head: 5.88% // Increases project coverage by +5.88% :tada:

Coverage data is based on head (ecaf0ec) compared to base (bb036f8). Patch coverage: 59.57% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #227      +/-   ##
=========================================
+ Coverage    0.00%   5.88%   +5.88%     
=========================================
  Files           8       8              
  Lines         860     900      +40     
=========================================
+ Hits            0      53      +53     
+ Misses        860     841      -19     
- Partials        0       6       +6     

Impacted Files	Coverage Δ
server/configuration.go	24.44% <58.33%> (+24.44%)	:arrow_up:
server/plugin.go	21.23% <60.00%> (+21.23%)	:arrow_up:

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[DHaussermann]

Thanks @mickmister I will keep an eye on this discussion 👍

[Szymongib]

For visibility, we are working together with IT to get Zoom apps published so that this can be easily tested on Test env.

[Szymongib]

Hey @dipak-demansol, yes I am aware of that. As mentioned in the comment above we need to publish the Zoom application to Zooms' marketplace and we are facing some difficulties with it.

I will ping you back when we hopefully get it done.

[mattermod]

This PR has been automatically labelled "stale" because it hasn't had recent activity. A core team member will check in on the status of the PR to help with questions. Thank you for your contribution!

[hanzei]

@Szymongib Do you plan to continue working on this?