refactor(router): move db models into separate crate and refactoring around it (#125)

crates/storage_models/src/errors.rs

@@ -0,0 +1,16 @@
+#[derive(Debug, thiserror::Error)]
+pub enum DatabaseError {
+    #[error("An error occurred when obtaining database connection")]
+    DatabaseConnectionError,
+    #[error("The requested resource was not found in the database")]
+    NotFound,
+    #[error("A unique constraint violation occurred")]
+    UniqueViolation,
+    #[error("No fields were provided to be updated")]
+    NoFieldsToUpdate,
+    #[error("An error occurred when generating raw SQL query")]
+    QueryGenerationFailed,
+    // InsertFailed,
+    #[error("An unknown error occurred")]
+    Others,
+}