feature request: support delete on non-integer-pk table

[vanliu-tx]

There are many tables with string primary key, now delete statement of this kind of table is not supported by flink databend sink.

[hantmac]

I checked the release history and code, now the flink databend sink has support string primary key.
For example, you can use the _id which is string type of mongodb as primary key, the demo flink sql is:

create table d_customers (_id String, customer_id INT,name String,address String, PRIMARY KEY (`_id`) NOT ENFORCED)
with ('connector' = 'databend',
'url'='databend://localhost:8000',
'username'='databend',
'password'='databend',
'database-name'='default',
'table-name'='customers',
'sink.batch-size' = '1',
'sink.ignore-delete' = 'false',
'sink.flush-interval' = '1000',
'sink.primary-key' = '_id',
'sink.max-retries' = '3');

Just use the latest version to test it.