Add support for copy.existing.namespace.regex and pipeline config to mongo-cdc

[bobby-richard]

Problem: I need to capture data from multiple tenant databases in the same mongodb cluster

The connector already allowed you to capture data from multiple databases/collections, but this was not very useful without the ability to filter. The copy.existing.namespace.regex setting already exists in the kafka source connector and does exactly this. So this PR just exposes the existing setting to the flink connector.

[leonardBang]

Thanks @bobby-richard for the contribution, @Jiabao-Sun Could you help review this PR?

[Jiabao-Sun]

@leonardBang OK

[Jiabao-Sun]

Thanks @bobby-richard, It's a nice improvement. This setting was not exposed before because multiple databases and collections are complicated for users.

The copy.existing.namespace.regex setting to provide a regular expression that matches specific collections by their namespace, but there is no subscription for these collection changes.

If we need to improve the support of multiple databases and collections, I think we should also expose pipeline configuration for MongoDBTableSource according to the multiple-source-example.

https://github.com/ververica/flink-cdc-connectors/blob/e19b78691ece0af61db42800fb97be64242a77e9/flink-connector-mongodb-cdc/src/main/java/com/ververica/cdc/connectors/mongodb/MongoDBSource.java#L181-L188

[bobby-richard]

Sounds good @Jiabao-Sun, I will expose pipeline as well.

[bobby-richard]

@Jiabao-Sun Exposed pipeline configuration as well. Nice catch!

[Jiabao-Sun]

Thanks @bobby-richard, it LGTM.
Hi @leonardBang, do you have other suggestions?

[bobby-richard]

@leonardBang @Jiabao-Sun any updates?

[Jiabao-Sun]

@leonardBang @Jiabao-Sun any updates?

Thanks @bobby-richard, it's a good enhencement that we can subscribe and filter multiple databases and collections.

@wuchong @leonardBang Do you have any suggestions?

[leonardBang]

Thanks @Jiabao-Sun for the contribution, could we use databaselist and collectionList filter and then transfer to underlying copy.existing.namespace.regex here for unification consideration? other parts looks good to me.

[Jiabao-Sun]

closed #940