Add comprehensive OpenAPI specifications to all FastAPI endpoints

[Copilot]

This PR enhances the DECODE Cloud UserAPI by adding comprehensive OpenAPI specifications to all FastAPI endpoints, ensuring complete API documentation compliance.

Changes Made

🎯 Core Requirements Implemented

All 17 FastAPI endpoints across 6 files now include the required OpenAPI parameters:

• response_model: Proper Pydantic models for all response types
• status_code: Explicit HTTP status codes (200, 201, 204, etc.)
• responses: Multiple response scenarios including error cases
• description: Enhanced, detailed endpoint descriptions

📋 Endpoints Updated

• Main App (api/main.py): Root welcome endpoint
• Jobs (api/endpoints/jobs.py): 5 endpoints for job management
• Files (api/endpoints/files.py): 8 endpoints for file operations
• Authentication (api/endpoints/auth.py): 3 endpoints for user auth
• User Info (api/endpoints/auth_get.py): 2 endpoints for user data
• Internal (api/endpoints/job_update.py): 1 endpoint for job status updates

🏗️ Infrastructure Improvements

• Common Response Models: Created ErrorResponse and MessageResponse for consistent error handling
• Enhanced Examples: Added realistic schema_extra examples to all Pydantic models:
  • Job: Complete job lifecycle example with all fields
  • User: User profile with groups
  • TokenResponse: JWT token with expiration
  • FileInfo: File metadata example
  • FileHTTPRequest: Pre-signed URL structure
  • JobUpdate: Status update example

📚 Documentation Benefits

The generated OpenAPI specification now provides:

• Complete API Documentation: Every endpoint fully documented with parameters and responses
• Interactive Examples: Realistic request/response examples in FastAPI's /docs interface
• Client Generation Ready: Comprehensive schema for automatic client library generation
• Error Handling Guide: Clear documentation of all possible error responses

🔒 Quality Assurance

• ✅ Zero breaking changes - full backward compatibility maintained
• ✅ All syntax verified and tested
• ✅ Follows FastAPI best practices
• ✅ Consistent error response format across all endpoints

This enhancement significantly improves the developer experience by providing comprehensive, interactive API documentation that will be automatically generated and displayed in FastAPI's built-in documentation interface.

Fixes #25.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[Copilot]

@nolan1999 👋 This repository doesn't have Copilot instructions. With Copilot instructions, I can understand the repository better, work faster and produce higher quality PRs.

I can generate a .github/copilot-instructions.md file for you automatically. Click here to open a pre-filled issue and assign it to me. I'll write the instructions, and then tag you for review.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
api
__init__.py	0	0	100%
database.py	13	4	69%	22–26
dependencies.py	51	21	59%	32–37, 59, 69, 78–97, 103–115
exceptions.py	9	2	78%	10, 18
main.py	25	3	88%	36, 54, 59
models.py	43	0	100%
settings.py	77	23	70%	15–18, 28–29, 65–69, 74, 78, 86, 95–101, 104–109, 112, 121
tags.py	1	0	100%
api/core
__init__.py	0	0	100%
aws.py	5	1	80%	7
filesystem.py	225	33	85%	35, 48, 51, 54, 59, 66, 72, 87, 90, 93, 96, 99, 109, 114, 194, 196–205, 219, 291, 348, 356–368, 379, 410
notifications.py	27	13	52%	14, 28–29, 32–52
api/crud
__init__.py	0	0	100%
job.py	71	4	94%	30, 56, 144–145
api/endpoints
__init__.py	0	0	100%
auth.py	66	49	26%	36–75, 91–118, 137–174
auth_get.py	15	2	87%	27, 49
files.py	53	6	89%	32–33, 53–54, 141, 163
job_update.py	30	2	93%	34, 51
jobs.py	35	2	94%	29, 118
api/schemas
__init__.py	0	0	100%
common.py	9	0	100%
file.py	28	0	100%
job.py	117	9	92%	27, 33, 36, 42, 47, 76, 85, 91, 93
job_update.py	8	0	100%
token.py	6	0	100%
user.py	15	0	100%
TOTAL	929	174	81%

Tests	Skipped	Failures	Errors	Time
128	0 💤	0 ❌	0 🔥	9m 40s ⏱️