feat(core): DSP-230 basic config service implementation

[ryanulit]

Proposed Changes

This is the initial POC of the Config Service, with all code located in the platform repo for the sole purpose of ease of implementation. There are still ongoing discussions about having the code live in DSP with some sort of shim/plugin functionality provided by the platform to enable loading the custom PEP/service configs.

Goals of the Config Service:

• Use Protobuf definitions with custom options to define config fields and their metadata in a single file
• Config protobuf defines the schema for configuration fields
• Internal PEP/Service uses the Config protobuf definition to create their unique configurations
• PEP/Service configs stored in a new schema of existing Postgres DB
• Admin Web UI forms can be dynamically generated from Proto definitions
• gRPC Service allows Admin to create/modify configs from Admin Web UI or CLI

Whimsical:

• https://whimsical.com/config-service-poc-Tqc88zFU4vuqpicsG2pxW8

Checklist

• I have added or updated unit tests
• I have added or updated integration tests (if appropriate)
• I have added or updated documentation

Testing Instructions