feat: public APIs

[cre8ivejp]

To be able to manage the flags and other features outside of the console.

[kentakozuka]

What we want

• Giving up command
• Diff b/w versions
• We can still go with gRPC
  • Simplifying APIs is necessary in any case (OpenAPI／gRPC).
• Start from Feature object

milestones

1. Design auth
   • API Token
2. Simplify gRPC API
   1. Start from Feature
      1. Create new APIs
         1. Create/Get/Update/Delete
   2. Give up commands

--- Phase 2

1. (if necessary) implement HTTP with OpenAPI
2. Do the same for all entities

[kentakozuka]

System design

(Updated 2024-06-17)

sequenceDiagram
    3rdParty->>+APIGateway: GetFeature (gPRC)
    APIGateway->>+Backend (Feature service): GetFeature (gRPC)