add dummy query builder

src/lib.rs

@@ -75,10 +75,16 @@ fn impl_from_args_struct(
         None => format_ident!("{}DB", name),
     };
 
+    let name_query_builder = format_ident!("{}QueryBuilder", name_db);
+
     let db_doc = format!(
         "An in-memory database for storing instances of [`{}`], generated by `#[derive(VennDB)]`.",
         name
     );
+    let query_doc = format!(
+        "A query builder for querying instances of [`{}`] in a [`{}`] database.",
+        name, name_db
+    );
     quote! {
         #[doc=#db_doc]
         #vis struct #name_db {
@@ -101,12 +107,22 @@ fn impl_from_args_struct(
             #vis fn is_empty(&self) -> bool {
                 self.rows.is_empty()
             }
+
+            /// Query the database using a query builder.
+            #vis fn query(&self) -> #name_query_builder {
+                #name_query_builder { db: self }
+            }
         }
 
         impl Default for #name_db {
             fn default() -> Self {
                 Self::new()
             }
         }
+
+        #[doc=#query_doc]
+        #vis struct #name_query_builder<'a> {
+            db: &'a #name_db,
+        }
     }
 }