[Parent issue] Support for Apache Pulsar

Since there is a continious demand for it,
just an overview for current state of Support for Apache Pulsar:

- when looking into beams i/o connector matrix **pulsar is not listed yet**:
https://beam.apache.org/documentation/io/connectors/

- but there is a **sdk package**
Package org.apache.beam.sdk.io.pulsar
https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/pulsar/package-summary.html

- in v2.39 of beam a relatively **basic pulsar io** was introduced:
Implemented Apache PulsarIO https://beam.apache.org/blog/beam-2.39.0/
for details see:
https://issues.apache.org/jira/browse/BEAM-8218

- there are some **open issues** in beam for pulsar:
https://github.com/apache/beam/issues?q=is%3Aissue+pulsar+is%3Aopen

- #30688
- #30152
- #22054
- #22027
- #22025
- #21714
- #21560
- #31079

- there were also some non merged pull request marked as stale and **automatically closed, which may be worth to have a look on**
https://github.com/apache/beam/pulls?q=is%3Apr+pulsar+is%3Aclosed+label%3Astale

- #26410
- #22375
- #22028
- #22026
- #17473
- #16749

- in general it would be a good longterm target, to reach the same quality of integration in Beam as there is for Kafka

Start with the Apache Pulsar SDK package and the Beam I/O connector matrix, then review the linked open issues (#30688, #30152, #22054, #22027, #22025, #21714, #21560, and #31079). The stale closed pull requests may provide additional context. Done would mean defining and implementing a Pulsar integration with quality comparable to Kafka.

Written by the indexing model from the issue text.