Added configuration to enable video downloads through an external AllTube instance. This provides an alternative download link and displays it in error messages when videos fail to load. Enhances user experience by offering external download support.
This PR adds two new config option, to pass a PO token (config 'po_token') and
a visitor ID (config 'visitor_data') to Youtube. These two strings are required
to play videos using the WEB client.
Warning: These strings gives much more identifiable information to Google!
If the po_token setting is filled in, then the WEB client is used. If not, the
Android client is used. TvHtml5ScreenEmbed will still be used as a fallback.
Script for generating po_token and visitor_data:
https://github.com/iv-org/youtube-trusted-session-generator
Helps with issue 4734
Unlike the other migrations, this one uses a bare table name to specify the table. This means it looks in the default search path. Unfortunately, the out of box search path is:
1. Schema with the same name as the user
2. Public
Because of this, if a schema exists with the same name as the DB user, the playlist_videos table will get created in _that_ schema, rather than the public schema, and then the grant statement will fail with an error like below if check_table is enabled as it keeps trying to create the table but failing on the grant statement:
```
2022-01-22 02:27:42 UTC [info] check_table: check_table: CREATE TABLE playlist_videos
Unhandled exception: relation "public.playlist_videos" does not exist (PQ::PQError)
from /usr/share/crystal/src/primitives.cr:266:3 in 'handle_error'
from lib/pg/src/pq/connection.cr:184:9 in 'handle_async_frames'
from lib/pg/src/pq/connection.cr:162:7 in 'read'
from lib/pg/src/pq/query.cr:53:14 in 'exec_all'
from lib/db/src/db/database.cr:126:9 in '__crystal_main'
from /usr/share/crystal/src/crystal/main.cr:110:5 in 'main'
from src/env/__libc_start_main.c:94:2 in 'libc_start_main_stage2'
2022-01-22 02:27:43 UTC [info] check_table: check_table: CREATE TABLE playlist_videos
Unhandled exception: relation "public.playlist_videos" does not exist (PQ::PQError)
from /usr/share/crystal/src/primitives.cr:266:3 in 'handle_error'
from lib/pg/src/pq/connection.cr:184:9 in 'handle_async_frames'
from lib/pg/src/pq/connection.cr:162:7 in 'read'
from lib/pg/src/pq/query.cr:53:14 in 'exec_all'
from lib/db/src/db/database.cr:126:9 in '__crystal_main'
from /usr/share/crystal/src/crystal/main.cr:110:5 in 'main'
from src/env/__libc_start_main.c:94:2 in 'libc_start_main_stage2'
```
* Untrack config.yml
`config/config.yml` has been untracked and moved to `config/config.example.yml`.
The Dockerfile has been updated to copy all `config/config.*` files and to try
to move `config/config.example.yml` to `config/config.yml`. If a user supplied
`config/config.yml` exists it is not overwritten.
* Update Dockerfile to use `shard.lock`
* Fix tests
