Replace arut's nginx-dav-ext-module with mid1221213's fork

[Ian-Marcel]

Background

The current angie-module-dav-ext package is built from
arut/nginx-dav-ext-module,
which has been unmaintained for over 8 years. Given that the module is
largely feature-complete, this is not necessarily a concern in itself —
however, several bugs remain unaddressed in the original.

Issues with the current upstream

• PROPFIND fails on broken symlinks — requests against non-existing
  symlink targets return an error instead of being handled gracefully.
• Hidden (dot-prefixed) files and directories are not handled correctly —
  any item beginning with . (e.g. .gitignore, .config/) causes
  unexpected behavior.
• Invalid UNLOCK tokens return 412 — a spec-incorrect response for
  bad LOCK tokens.

Proposed change

Replace the source with
mid1221213/nginx-dav-ext-module,
a fork that resolves all three issues above. The fork itself has not seen
activity since its 2021 release, but given the module's maturity and the
targeted nature of the fixes, this is not a practical concern.

Request

Would you consider switching the angie-module-dav-ext build source to
the mid1221213 fork? It is API-compatible with the original and the
changes are limited in scope, making the regression risk low.

[Ligature60]

We'll look into this. Thank you for the suggestion.