Respect sharing.federation.allowHttpFallback config option

[mrow4a]

This MR in general help local testing for federated sharing :

• catches exception that allow fallback from https->http
• add some more unit tests testing tryHttpPostToShareEndpoint

Reasons:

• without this MR, exception is shown to the user:
  cURL error 60: SSL certificate problem: self signed certificate
• now, better exception is shown as request gets properly handled:
  server cannot be reached
• now, with the config sharing.federation.allowHttpFallback set, allows to create federated share.

Do we need some documentation for this config (developer docs) ?

occ config:system:set sharing.federation.allowHttpFallback --value true --type boolean

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[codecov]

Codecov Report

Merging #37153 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master   #37153   +/-   ##
=========================================
  Coverage     64.85%   64.86%           
  Complexity    19136    19136           
=========================================
  Files          1267     1267           
  Lines         74895    74895           
  Branches       1331     1331           
=========================================
+ Hits          48575    48578    +3     
+ Misses        25928    25925    -3     
  Partials        392      392           

Flag	Coverage Δ	Complexity Δ
#javascript	54.14% <ø> (ø)	0.00 <ø> (ø)
#phpunit	66.05% <100.00%> (+<0.01%)	19136.00 <0.00> (ø)

Impacted Files	Coverage Δ	Complexity Δ
apps/federatedfilesharing/lib/Notifications.php	43.67% <100.00%> (+1.89%)	45.00 <0.00> (ø)

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[VicDeo]

Looks good