POST endpoint for importing m3u playlists - #2078 (#2273)

* wip: API endpoint for creating playlists from m3u files

* wip: get user id from context

* temporarily disable failing test

* custom logic for playlist route to accomodate m3u content type

* incorporate playlist parsing into existing logic in core

* re-enable test

* fix locally failing test

* Address requested changes.

* Improve ImportFile tests.

* Remove ownerID as a parameter of ImportM3U.

* Write tests for ImportM3U.

* Separate ImportM3U test into two.

* Test OwnerID and playlist Name.

---------

Co-authored-by: Sam Watson <SwatsonCodes@users.noreply.github.com>
Co-authored-by: caiocotts <caio@cotts.com.br>

tests/fixtures/playlists/pls-post-with-name.m3u

@@ -0,0 +1,4 @@
+#PLAYLIST:playlist 1
+tests/fixtures/test.mp3
+tests/fixtures/test.ogg
+file:///tests/fixtures/01%20Invisible%20(RED)%20Edit%20Version.mp3

tests/fixtures/playlists/pls-post.m3u

@@ -0,0 +1,3 @@
+tests/fixtures/test.mp3
+tests/fixtures/test.ogg
+file:///tests/fixtures/01%20Invisible%20(RED)%20Edit%20Version.mp3