refactor(nextcloud)!: Migrate to DAV v2 endpoint for WebDAV

[provokateurin]

Replaces #2306
Should help with #2308 and #718 as those require using the v2 endpoints.

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.

Project coverage is 28.79%. Comparing base (a01e746) to head (af1f3d3).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/nextcloud/lib/webdav.dart	71.42%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2557   +/-   ##
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  Coverage   28.79%   28.79%           
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  Files         370      370           
  Lines      136490   136496    +6     
=======================================
+ Hits        39296    39300    +4     
- Misses      97194    97196    +2     

Flag	Coverage Δ		*Carryforward flag
account_repository	98.47% <ø> (ø)
cookie_store	99.48% <ø> (ø)		Carriedforward from a01e746
dashboard_app	96.05% <ø> (ø)
dynamite	31.05% <ø> (ø)		Carriedforward from a01e746
dynamite_end_to_end_test	61.69% <ø> (ø)		Carriedforward from a01e746
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from a01e746
interceptor_http_client	97.18% <ø> (ø)		Carriedforward from a01e746
neon_dashboard	96.05% <ø> (ø)		Carriedforward from a01e746
neon_framework	61.00% <ø> (ø)
neon_http_client	97.50% <100.00%> (ø)
neon_notifications	100.00% <ø> (ø)		Carriedforward from a01e746
neon_storage	94.66% <ø> (ø)
neon_talk	99.45% <ø> (ø)		Carriedforward from a01e746
nextcloud	24.26% <84.61%> (+<0.01%)	⬆️
notifications_app	97.40% <ø> (ø)
notifications_push_repository	98.11% <ø> (ø)
sort_box	90.90% <ø> (ø)		Carriedforward from a01e746
talk_app	98.94% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

Files with missing lines	Coverage Δ
..._client/lib/src/interceptors/csrf_interceptor.dart	100.00% <100.00%> (ø)
...xtcloud/lib/src/api/webdav/models/webdav_file.dart	100.00% <100.00%> (ø)
...nextcloud/lib/src/api/webdav/utils/webdav_uri.dart	100.00% <100.00%> (ø)
...es/nextcloud/lib/src/api/webdav/webdav_client.dart	94.70% <100.00%> (+0.02%)	⬆️
packages/nextcloud/lib/webdav.dart	75.00% <71.42%> (-25.00%)	⬇️

[provokateurin]

What we could do alternatively is to require the username to be passed when creating the WebDavClient. That would be a bit cleaner as then all the http.Request getters can be sync and we avoid doing a network request (since the consumer of the package might already know the username anyway like we do in Neon).

[Leptopoda]

This is also exactly what I thought.
Let's require the username at creation.

[provokateurin]

We could add an extension in the framework that would allow us to still call account.client.webdav without the username by automatically inserting the account username and internally using the underlying extension with the username parameter.
I don't think we really need it, but if you like it I can add it.