We're adding support in EDOT SDKs to configure TLS to secure OTLP and OpAMP endpoint connections. We're having documentation for Elastic APM agents on how to setup secure communication. We want to add documentation for EDOT SDKs too.

Taking EDOT Node.js as example we have the following configuration options mentioned in the configuration docs for OpAMP endpoint:

• ELASTIC_OTEL_OPAMP_CERTIFICATE: Path to a file, in PEM format, to override the built-in Node.js trusted CA certificates.
• ELASTIC_OTEL_OPAMP_CLIENT_CERTIFICATE: Path to a file with a client certificate or certificate chain, in PEM format, to use for mTLS.
• ELASTIC_OTEL_OPAMP_CLIENT_KEY: Path to file with the private key used for the Certificate Signing Request (CSR) to create the client certificate. Used for mTLS.

as well as for the OTLP endpoint in the configuration reference table:

• OTEL_EXPORTER_OTLP_CLIENT_KEY: (Ref) Client private key for mTLS communication. Also supports signal-specific OTEL_EXPORTER_OTLP_{signal}_CLIENT_KEY.
• OTEL_EXPORTER_OTLP_CLIENT_CERTIFICATE: (Ref) The trusted certificate to use when verifying a server's TLS credentials. Also supports signal-specific OTEL_EXPORTER_OTLP_{signal}_CLIENT_CERTIFICATE.

We should also add the TLS support to the feature overview table.