feat: integrate thiserror

parser/src/validation.rs

@@ -1,17 +1,25 @@
 
 use std::collections::HashSet;
+use thiserror::Error;
 
 use minisql::{operation::{ColumnSelection, Condition, InsertionValues, Operation}, schema::TableSchema, type_system::{DbType, IndexableValue, Value}};
 
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 pub enum ValidationError {
+    #[error("table {0} does not exist")]
     TableDoesNotExist(String),
+    #[error("table {0} already exists")]
     TableExists(String),
+    #[error("column {0} does not exist")]
     ColumnDoesNotExist(String),
+    #[error("bad column position {0}")]
     BadColumnPosition(usize),
+    #[error("duplicate column {0}")]
     DuplicateColumn(String),
+    #[error("type mismatch")]
     TypeMismatch,
+    #[error("value for required column {0} is missing")]
     ValueForRequiredColumnIsMissing(String)
 }