Define Configuration Schema & Defaults

[JoTurk]

We should create a single source of truth config struct with sensible defaults and name convention, easy to extension in the future without breaking changes.

Options i have in mind.

1. One monolithic config
   One Toml, JSON or even XML config file with the ability to configure what file to load when starting the service using a flag like --config/c.
   If we go with JSON i prefer if we support JSON5 because of the ability to add comments.

• Pros: Simple. easy to move.
• Cons: Big struct? too verbose.

2. One config per module.
   For example: storage.json, turn.json etc
   It'll maybe make more sense when we make the plugin system and attachable modules.

• Pros: Ownership & cohesion
• Cons: More verbose and more complex for the end user.

3. Optional: the ability to overwrite configs via arguments or env vars

• Pros: It will provide sensible deployment in some situation.
• Cons: Even more complex logic, harder to translate nested options and some types.

(we're open to any other option)

I think:

1. We shouldn't store any secrets in the config file one way or another.
2. We shouldn't tolerate incorrect or invalid config, it should fail fast, if the user types incorrect config key it should try to find the correct one and suggest it.
3. If we support overriding configs via env, we should add a prefix to all the configurations ION_ so it doesn't cause conflations with other applications in weird setups.
4. We should design the config in a way that it's possible to be over-ridable while the application is running or maybe even fully provided through the wire / external API. I don't think we should support that now, but we should design it in a way that this is possible.

Tasks:

• Define a basic config structure module and naming conviction.
• Define how to store and load config.
• Define the initial service config, (logging, metrics, tracing, signaling, sfu, webrtc, network).
• Chose a sensible default for a SFU.
• Document the configs in the code itself and provide help command, and clear strict errors for wrong configs.
• Implement config loading. and the basic configuration.