doc: add missing docstring + add missing feature to README (#57)

src/fastapi_toolsets/exceptions/__init__.py

@@ -1,3 +1,5 @@
+"""Standardized API exceptions and error response handlers."""
+
 from .exceptions import (
     ApiError,
     ApiException,

src/fastapi_toolsets/exceptions/exceptions.py

@@ -87,6 +87,12 @@ class InsufficientRolesError(ForbiddenError):
     )
 
     def __init__(self, required_roles: list[str], user_roles: set[str] | None = None):
+        """Initialize the exception.
+
+        Args:
+            required_roles: Roles needed to access the resource
+            user_roles: Roles the current user has, if known
+        """
         self.required_roles = required_roles
         self.user_roles = user_roles
 
@@ -130,6 +136,11 @@ class NoSearchableFieldsError(ApiException):
     )
 
     def __init__(self, model: type) -> None:
+        """Initialize the exception.
+
+        Args:
+            model: The SQLAlchemy model class that has no searchable fields
+        """
         self.model = model
         detail = (
             f"No searchable fields found for model '{model.__name__}'. "

src/fastapi_toolsets/exceptions/handler.py

@@ -12,6 +12,25 @@ from .exceptions import ApiException
 
 
 def init_exceptions_handlers(app: FastAPI) -> FastAPI:
+    """Register exception handlers and custom OpenAPI schema on a FastAPI app.
+
+    Installs handlers for :class:`ApiException`, validation errors, and
+    unhandled exceptions, and replaces the default 422 schema with a
+    consistent error format.
+
+    Args:
+        app: FastAPI application instance
+
+    Returns:
+        The same FastAPI instance (for chaining)
+
+    Example:
+        from fastapi import FastAPI
+        from fastapi_toolsets.exceptions import init_exceptions_handlers
+
+        app = FastAPI()
+        init_exceptions_handlers(app)
+    """
     _register_exception_handlers(app)
     app.openapi = lambda: _custom_openapi(app)  # type: ignore[method-assign]
     return app