[cmd/opampsupervisor]: Allow configuring the agent description

[BinaryFissionGames]

Component(s)

cmd/opampsupervisor

Is your feature request related to a problem? Please describe.

We would like to be able to associate extra user-specified information with the agent. In our case, we have a user that would like to be able to add extra identifying information (a separate unique ID) to OpAMP's agent description message.

The spec allows for a user to specify necessary identifying attributes, as well as any non-identifying attributes a user would like to associate with the agent. See: https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agentdescriptionidentifying_attributes

Describe the solution you'd like

The supervisor should support configuring extra agent_description attributes.

The configuration would end up looking like this:

agent:
  description:
    identifying_attributes:
      key: val
    non_identifying_attributes:
      key: val

Where key and val are arbitrary key-value pairs.

These key-value pairs will be injected by the supervisor into the agent description retrieved during the bootstrap process. The values in the supervisor config will override the ones in the collector's agent description.

Describe alternatives you've considered

No response

Additional context

We discussed allowing the opamp extension to configure identifying attributes, but decided that it was susceptible to mis-configuration (identifying attributes must be on the agent's self-telemetry).

For more context, see:
#32644

[github-actions]

Pinging code owners:

• cmd/opampsupervisor: @evan-bradley @atoulme @tigrannajaryan

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