v6.0.0-RC1

Change log:

b0bf59f Upgrade to SWS 4.0.0-RC1; prepare for release
cd910a1 Migrate event module tests to JUnit 5
c922905 GH-3912: Handler: ignore Groovy generated methods
beef2e6 Use unique consumer groups in KafkaDslKotlinTests
0951738 Upgrade dependencies to be ready for release
64f0e73 GH-3897: Deprecate ChannelSecurityInterceptor
ff076b6 GH-3902: Add Kotlin Coroutines Support (#3905)
cfeaeca GH-3421: Resolve throws Exception; in the API
a08713f Migrate Cassandra extension project (#3913)
83f2a9c Migrate Groovy DSL extension project (#3914)
fe06fbc Fix XmppConnFactoryBeanTests config for parser
b7dd7d1 Fix RetryAdviceParser for the latest spring-retry
e1d62b5 Observation docsL: single DocsGeneratorCommand
5ccfcbd Fix SftpSession for host:port resolution
f7dd876 INT-3333: Return empty list as is from DB gateway (#3907)
6641b1f GH-3664: Re-enable JavaScript support via GraalVM (#3911)
1dd8b6b Add jackson-databind to AMQP module for tests
c68ec19 Fix HttpDslTests for latest Spring Security
f4d7c4f INT-2086: JMS TemporaryTopic when replyPubSub
a30dc10 Improve messaging gateway mapping
a9f511c Remove reflection handling for kotlin.Unit class
daaa30e Make replyContainer as bean in Kafka tests
f24fbd9 Add documentation for Observability (#3896)
a667171 Use unique Kafka consumer groups in tests
6b31d97 Remove spring-integration-gemfire module
fb1c89f AsyncGatewayTests: Fix to currentThread() method
5fadaf5 GH-3635: Add Future & Mono to gateway (#3899)
0eb6ae1 Fix new classes and packages tangles (#3898)
6246c9f Remove superfluous space in IntegrationFlowBuilder (#3901)
6ce61ed Disable ResKnownHostsSerKeyVerifierTests on CI
82e3073 Remove unused import from known_hosts test class
e32a502 Use hashed host for known_hosts tests
4aa2f91 GH-3572: Migrate SFTP from jsch to sshd-sftp (#3892)
6917663 Adapt to the latest SF changes
26816a3 GH-3626: RabbitMQ Stream Support (#3895)
cbfa150 GH-3661: Fix Javadocs for RetryingMLA