ArangoCollectionModule Fix and Enhancements

[clintmorgan]

• [ ] DropCollectionAsync: Line 81 - Remove closing parenthesis prefixing url encoded collection name From: ApiPath(database, $"collection/){UrlEncode(collection)}") To: ApiPath(database, $"collection/{UrlEncode(collection)}")

• [ ] Perhaps rename method to DropAsync to match naming conventions (same for IArangoCollectionModule)

• [ ] Add 2 additional support methods and expose through IArangoCollectionModule

        public async Task<bool> ExistAsync(ArangoHandle database, string collection,
            CancellationToken cancellationToken = default)
        {
            var collections = await ListAsync(database, cancellationToken);

            return collections.Contains(collection);
        }

        public async Task<ArangoCollection> GetAsync(ArangoHandle database, string collection,
            CancellationToken cancellationToken = default)
        {
            return await SendAsync<ArangoCollection>(
                HttpMethod.Get, 
                ApiPath(database, $"collection/{UrlEncode(collection)}"),
                null, database.Transaction, cancellationToken: cancellationToken);
        }