Method modify_or_insert_with_value

src/models/common.rs:585–600

works exactly like `modify_or_insert`, but takes a value `T`, which is passed to both closures (only one actually runs, so only passed to one of them), which is not possible with `modify_or_insert` because of Rust's borrow checking rules

(&self, k: K, v: T, modify: M, insert: I)

    // closures (only one actually runs, so only passed to one of them), which is not possible
    // with `modify_or_insert` because of Rust's borrow checking rules
    pub fn modify_or_insert_with_value<M, I, T>(&self, k: K, v: T, modify: M, insert: I)
    where
        M: FnOnce(T, &mut V),
        I: FnOnce(T) -> V,
    {
        let index = self.hash_key(&k);
        let mut ht = self.hash_table_list[index].lock().unwrap();
        match ht.entry(k) {
            Entry::Occupied(mut entry) => {
                modify(v, entry.get_mut());
            }
            Entry::Vacant(entry) => {
                entry.insert(insert(v));
            }
        }
    }

    // This bool represents whether the key was found in the map or not.
    pub fn get_or_create_with_flag<F>(&self, k: K, f: F) -> (V, bool)