JSON API responses

[metachris]

📝 Summary

Make API calls return a JSON response, also JSON errors.

PR also fixes examples in the README.

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✅ I have run these commands

• make lint
• make test
• go mod tidy

[Copilot]

Pull Request Overview

This PR standardizes API responses to use JSON format throughout the system API, replacing simple HTTP status codes with structured JSON responses for both success and error cases.

• Implements consistent JSON response format for all API endpoints
• Introduces structured error responses with status codes and messages
• Adds helper methods for standardized JSON response handling

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
systemapi/server.go	Adds JSON response helper methods and converts all endpoints to return structured JSON responses
systemapi/middleware.go	Updates basic auth middleware to return JSON error responses
systemapi/constants.go	Defines HTTP header and media type constants for consistent usage
systemapi-config.toml	Corrects filename reference in configuration comments
README.md	Updates example commands to use HTTPS and corrects configuration references

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[Copilot]

The httpErrorResp struct is referenced here but not defined in this file. This creates a dependency on server.go that should be avoided. Consider moving the struct to a shared location like constants.go or creating a dedicated types file.

[Copilot]

The nolint comment suggests awareness of a performance issue with fmt.Sprint. Consider using strconv.Itoa(len(content)) instead, which is more efficient for integer-to-string conversion.