feat(backend): add the db connection

backend/database/models/classification.py

@@ -0,0 +1,14 @@
+from ..connection import DatabaseConnection
+
+class Classification:
+    def __init__(self, classification_name: str):
+        self.classification_name = classification_name
+
+    def save(self, db: DatabaseConnection):
+        query = "INSERT INTO Classifications (ClassificationName) VALUES (?)"
+        db.execute_query(query, (self.classification_name,))
+
+    @classmethod
+    def get_all(cls, db: DatabaseConnection):
+        query = "SELECT * FROM Classifications"
+        return db.execute_query_with_return(query)