tonic feature add 'tls'

[Eshanatnight]

Fixes #608 .

Description

Uses the tls feature of tonic crate.
Read the certificate and key files from CONFIG and add tls_config to server.

Falls back on insecure connection if the certificate and or key is missing.

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This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.