oEmbed providers.json parsing

Description

As I wanted to check if #17462 can be fixed by using oEmbed I stumbled upon parsing issues in the oEmbed config parser. I used the official provider official providers.json from https://oembed.com/providers.json

The config parser throws an error and hinders Synapse from starting, when a provider in the providers.json does not contain the "schemes" key, IMO this should just throw a warning and not error out.

When a provider in the providers.json does not have a 'schemes' entry it can't be used directly in Matrix, as there is no URL pattern to match, these entries without 'schemes' are seemingly only there to signal that these websites have a discoverable oembed provider.

You can see which providers don't have schemes via this jq command: jq '.[] | select(.endpoints[].schemes == null)' providers.json

This is the current output of this command:
```json { "provider_name": "Beautiful.AI", "provider_url": "https://www.beautiful.ai/", "endpoints": [ { "url": "https://www.beautiful.ai/api/oembed", "discovery": true } ] } { "provider_name": "Box Office Buz", "provider_url": "http://boxofficebuz.com", "endpoints": [ { "url": "http://boxofficebuz.com/oembed", "discovery": true } ] } { "provider_name": "eduMedia", "provider_url": "https://www.edumedia-sciences.com/", "endpoints": [ { "url": "https://www.edumedia-sciences.com/oembed.json", "discovery": true }, { "url": "https://www.edumedia-sciences.com/oembed.xml", "discovery": true } ] } { "provider_name": "eduMedia", "provider_url": "https://www.edumedia-sciences.com/", "endpoints": [ { "url": "https://www.edumedia-sciences.com/oembed.json", "discovery": true }, { "url": "https://www.edumedia-sciences.com/oembed.xml", "discovery": true } ] } { "provider_name": "GloriaTV", "provider_url": "https://gloria.tv/", "endpoints": [ { "url": "https://gloria.tv/oembed/", "discovery": true } ] } { "provider_name": "Matterport", "provider_url": "https://matterport.com/", "endpoints": [ { "url": "https://my.matterport.com/api/v1/models/oembed/", "discovery": true, "formats": [ "json" ] } ] } { "provider_name": "PingVP", "provider_url": "https://www.pingvp.com/", "endpoints": [ { "url": "https://beta.pingvp.com.kpnis.nl/p/oembed.php", "discovery": true } ] } { "provider_name": "Rumble", "provider_url": "https://rumble.com/", "endpoints": [ { "url": "https://rumble.com/api/Media/oembed.{format}", "discovery": true } ] } { "provider_name": "Typlog", "provider_url": "https://typlog.com", "endpoints": [ { "url": "https://typlog.com/oembed", "discovery": true } ] } ```
The Parser also errors out for this spotify scheme: spotify:*. Again IMO this should probably just throw a warning instead of erroring out.

This would make it easier to just grab the latest providers.json from https://oembed.com and use it. (Which could make #9877 possible)

Steps to reproduce

add the providers.json from https://oembed.com/providers.json to your homeserver.yaml like so:
```
...
oembed:
disable_default_providers: true
additional_providers:
- providers.json
```
Start Synapse and immediately see the error that schemes are required
After you have removed the entries which contain no scheme, start synapse again and you'll see the error with the spotify scheme.

Homeserver

Synapse Version

1.113.0

Installation Method

Docker (matrixdotorg/synapse)

Database

Workers

I don't know

Platform

Not relevant for the issue but I use Debian on a Dedicated Server and Synapse runs inside Docker

Configuration

No response

Relevant log output

# This is the log output for the first issue:

Error in configuration at 'oembed.additional_providers.<item 0>.<item 282>.endpoints.<item 0>':
  'schemes' is a required property

# This is the log output for the second issue:

Error in configuration at 'oembed.additional_providers.<item 0>':
  Unsupported oEmbed scheme (spotify) for pattern: spotify:*

Anything else that would be useful to know?

The docs should probably be refined a bit https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html#oembed

I directly knew what the providers.json is and where to get it from, but I don't think that it is mentioned anywhere in the docs. Also a direct link to the providers.json that gets shipped by default would be helpful. I at first thought Synapse wouldn't ship one contrary to what the docs state, but the problem was I only searched for oembed, and @clokep pointed me to the link where it can be found https://github.com/element-hq/synapse/blob/develop/synapse/res/providers.json

element-hq / synapse