feat(api+testing): select todo by member_id and id

- Added test code coverage with `pytest-cov`
- Added comments for member model functions

backend/src/neo_neo_todo/models/member.py

@@ -91,6 +91,11 @@ async def insert_member(
 async def update_member_password(
     db: AsyncConnectionPool, id: int, password_hash: str
 ) -> bool:
+    """
+    Updates a member's password (their password_hash to be exact)
+
+    Returns a bool, True if successful and False if not
+    """
     async with db.connection() as conn:
         async with conn.cursor(row_factory=class_row(Member)) as curr:
             query = sql.SQL(
@@ -113,6 +118,11 @@ async def update_member_password(
 
 
 async def update_member_email_verified(db: AsyncConnectionPool, id: int) -> bool:
+    """
+    Updates a member's email verified status
+
+    Returns a bool, True if successful and False if not
+    """
     async with db.connection() as conn:
         async with conn.cursor(row_factory=class_row(Member)) as curr:
             query = sql.SQL(

backend/src/neo_neo_todo/models/todo.py

@@ -18,6 +18,11 @@ class Todo:
 async def select_todos(
     db: AsyncConnectionPool, member_id: int, complete: bool | None = None
 ) -> list[Todo]:
+    """
+    Select multiple Todo(s) from a member_id
+
+    Return a list of Todos (can be empty list)
+    """
     async with db.connection() as conn:
         async with conn.cursor(row_factory=class_row(Todo)) as curr:
 
@@ -43,3 +48,27 @@ async def select_todos(
             todos = await curr.fetchall()
 
             return todos
+
+
+async def select_todo(db: AsyncConnectionPool, id: int, member_id: int) -> Todo | None:
+    """
+    Find exactly one todo task that matches id and member_id
+    in todos list in PostgreSQL database
+
+    Return a Todo object or None
+    """
+    async with db.connection() as conn:
+        async with conn.cursor(row_factory=class_row(Todo)) as curr:
+            query = sql.SQL(
+                """
+                SELECT id, complete, due, task
+                    FROM todos
+                    WHERE id = (%s) AND member_id = (%s)
+                """
+            )
+
+            await curr.execute(query, (id, member_id))
+
+            member = await curr.fetchone()
+
+            return None if member is None else member