feat: enhance backend security and configuration

- Updated Dockerfile to improve security with a non-root user and added health checks.
- Modified docker-compose.yml to set containers as read-only, restrict ports to localhost, and implement health checks.
- Enhanced .env.example with additional environment variables for security and configuration.
- Improved FastAPI application with middleware for security headers, CORS, and body size limits.
- Refactored authentication flow in auth.py to include state validation and improved error handling.
- Added rate limiting to various endpoints to prevent abuse.
- Updated researcher and publication handling to ensure better validation and error management.

backend/app/db/repositories/researcher_repository.py

@@ -2,13 +2,24 @@ from sqlalchemy.orm import Session
 from app.db.models import Researcher
 from sqlalchemy.sql import func
 
+# ---------------------------------------------------------
+# Repositorio de investigadores
+# ---------------------------------------------------------
 
 class ResearcherRepository:
 
+    # ---------------------------------------------------------
+    # Función auxiliar: obtener investigador por ORCID ID
+    # ---------------------------------------------------------
+
     @staticmethod
     def get_by_orcid(db: Session, orcid_id: str):
         return db.query(Researcher).filter(Researcher.orcid_id == orcid_id).first()
 
+    # ---------------------------------------------------------
+    # Función auxiliar: crear un nuevo investigador
+    # ---------------------------------------------------------
+
     @staticmethod
     def create(db: Session, orcid_id: str, name: str = None):
         researcher = Researcher(orcid_id=orcid_id, name=name)
@@ -17,6 +28,10 @@ class ResearcherRepository:
         db.refresh(researcher)
         return researcher
 
+    # ---------------------------------------------------------
+    # Función auxiliar: actualizar la última sincronización
+    # ---------------------------------------------------------
+
     @staticmethod
     def update_last_sync(db: Session, researcher: Researcher):
         researcher.last_sync_at = func.now()