Refactor session ID handling and improve error management

- Introduced `SessionId` newtype for validated session identifiers, ensuring safety against path traversal attacks.
- Updated session repository methods to accept `SessionId` instead of raw strings, enhancing type safety.
- Removed redundant error handling in repository methods by leveraging the new `Error` type from `zesdex_utils`.
- Simplified atomic JSON write operations by eliminating unnecessary error conversions.
- Enhanced integer casting with a new `CastOr` trait for safer narrowing conversions.
- Removed deprecated error handling code and consolidated error types across the codebase.
- Updated HTTP handlers to utilize the new session ID validation, improving overall robustness.

crates/zesdex-cms/src/domain/error.rs

@@ -1,116 +1,41 @@
 //! Domain error types for the CMS crate.
 //!
 //! Typed error enums for repository and service operations.
-//! `From` impls connect `std::io::Error` and `serde_json::Error` into
-//! `RepositoryError`, and `RepositoryError` into `ServiceError`.
+//! The `RepositoryError` type is re-exported from `zesdex_utils::Error`,
+//! which has all needed variants: `NotFound`, `Conflict`, `Io`, `Serde`,
+//! `InvalidId`, `Other`, etc.
+//!
+//! `From` impls are generated by `thiserror::Error` derive macros.
 //! Anyhow's blanket `From<E: StdError + Send + Sync + 'static>`
 //! covers conversion to `anyhow::Error` for downstream code.
 
-use std::fmt;
-
 // ---------------------------------------------------------------------------
-// RepositoryError
+// RepositoryError (type alias)
 // ---------------------------------------------------------------------------
 
-/// Errors from repository / persistence operations in the CMS domain.
-#[derive(Debug)]
-pub enum RepositoryError {
-    /// The requested entity does not exist.
-    NotFound(String),
-    /// A conflict occurred (e.g. duplicate entry).
-    Conflict(String),
-    /// An I/O error occurred during persistence.
-    Io(std::io::Error),
-    /// A serialisation / deserialisation error occurred.
-    Serialization(serde_json::Error),
-    /// The supplied identifier is invalid (e.g. path traversal attempt).
-    InvalidId(String),
-    /// An error that could not be downcast to a specific variant.
-    Other(String),
-}
+/// Re-export shared repository error from `zesdex_utils`.
+pub use zesdex_utils::Error as RepositoryError;
 
-impl RepositoryError {
-    /// Convert an `anyhow::Error` to `RepositoryError` by attempting
-    /// downcast to known inner types.
-    pub fn from_anyhow(e: anyhow::Error) -> Self {
-        if let Some(ioe) = e.downcast_ref::<std::io::Error>() {
-            return RepositoryError::Io(std::io::Error::new(ioe.kind(), ioe.to_string()));
-        }
-        RepositoryError::Other(e.to_string())
-    }
-}
-
-impl fmt::Display for RepositoryError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            RepositoryError::NotFound(msg) => write!(f, "not found: {msg}"),
-            RepositoryError::Conflict(msg) => write!(f, "conflict: {msg}"),
-            RepositoryError::Io(e) => write!(f, "I/O error: {e}"),
-            RepositoryError::Serialization(e) => write!(f, "serialization error: {e}"),
-            RepositoryError::InvalidId(msg) => write!(f, "invalid id: {msg}"),
-            RepositoryError::Other(msg) => write!(f, "{msg}"),
-        }
-    }
-}
-
-impl std::error::Error for RepositoryError {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        match self {
-            RepositoryError::Io(e) => Some(e),
-            RepositoryError::Serialization(e) => Some(e),
-            _ => None,
-        }
-    }
-}
-
-impl From<std::io::Error> for RepositoryError {
-    fn from(e: std::io::Error) -> Self {
-        RepositoryError::Io(e)
-    }
-}
-
-impl From<serde_json::Error> for RepositoryError {
-    fn from(e: serde_json::Error) -> Self {
-        RepositoryError::Serialization(e)
-    }
-}
+// `From<RepositoryError> for anyhow::Error` is covered by anyhow's blanket
+// `impl<E: StdError + Send + Sync + 'static> From<E> for Error` — no
+// explicit impl needed.
 
 // ---------------------------------------------------------------------------
 // ServiceError
 // ---------------------------------------------------------------------------
 
 /// Errors from service / use-case operations in the CMS domain.
-#[derive(Debug)]
+#[derive(Debug, thiserror::Error)]
 pub enum ServiceError {
     /// A repository operation failed.
-    Repository(RepositoryError),
+    #[error("repository error: {0}")]
+    Repository(#[from] RepositoryError),
     /// The provided input is invalid.
+    #[error("invalid input: {0}")]
     InvalidInput(String),
     /// A generic error with a message.
+    #[error("{0}")]
     Other(String),
 }
 
-impl fmt::Display for ServiceError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            ServiceError::Repository(e) => write!(f, "repository error: {e}"),
-            ServiceError::InvalidInput(msg) => write!(f, "invalid input: {msg}"),
-            ServiceError::Other(msg) => write!(f, "{msg}"),
-        }
-    }
-}
-
-impl std::error::Error for ServiceError {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        match self {
-            ServiceError::Repository(e) => Some(e),
-            _ => None,
-        }
-    }
-}
-
-impl From<RepositoryError> for ServiceError {
-    fn from(e: RepositoryError) -> Self {
-        ServiceError::Repository(e)
-    }
-}
+// `From<ServiceError> for anyhow::Error` is covered by anyhow's blanket impl.