Proxy & TLS settings in OpAMPConnectionSettings, TelemetryConnectionSettings, and OtherConnectionSettings

[michel-laterman]

Connection settings that an OpAMP server offers should have some way to pass additional information that includes proxy settings and additional TLS settings.

TLS settings should TLS/mTLS settings defined in otel config tls.

Proxy settings may include:

• proxy url
• proxy headers
• proxy client certificate
• proxy TLS settings

Additionally I think that we should include other_settings in the definition of OpAMPConnectionSettings and TelemetryConnectionSettings to allow implementation to define their own additional settings.

[tigrannajaryan]

One thing I am a bit worried about is the complexity this imposes on the agents. I think we need to keep this to a minimum and only include settings that are required for successful connection and avoid adding desirable but necessarily required settings. For example looking at otel config tls, I see things like write_buffer_size. I don't think we need to add settings like this.

With that in mind I would like to see a draft of what the absolutely minimum of required settings would look like in proto form.

One other design consideration is to make sure OpAMPConnectionSettings, TelemetryConnectionSettings and OtherConnectionSettings are defined uniformly, with the exception of settings which are only applicable to a particular connection type (e.g. heartbeat_interval_seconds is unique to OpAMPConnectionSettings). A possible option would be to move all common settings to one proto message and include that from OpAMPConnectionSettings, TelemetryConnectionSettings and OtherConnectionSettings. That would be a breaking change, so we will need to discuss if it is worth it.

According to the rules we are allowed the breaking change since we are in Beta, but since we are so late in Beta stage, the bar is pretty high for breaking changes (cc @andykellr).

@michel-laterman if you can make a draft PR to show what the change would look like I think it would help the discussion.