Java 21 virtual thread support

[nmondal]

In submitting this contribution, I agree to the current Software AG contributor agreement as referred to here:
https://github.com/quartz-scheduler/contributing/blob/main/CONTRIBUTING.md

This PR...

How to Run

./gradlew -Djdk="<jdk 21 directory>"  test :quartz:test 

Changes

Adds a SimpleVirtualThreadPool to do a virtual thread support.

Checklist

• tested locally
• updated the docs
• added appropriate test
• signed-off on the above mentioned SoftwareAG contributor agreement via git commit -s on my commits.
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Known Issues

In java 21 - the following tests fail:

> Task :quartz:test

org.quartz.impl.jdbcjobstore.StdJDBCDelegateTest > testSelectSimpleTriggerWithDeleteBeforeSelectExtendedProps FAILED
    java.lang.ExceptionInInitializerError at StdJDBCDelegateTest.java:119
        Caused by: java.lang.reflect.InaccessibleObjectException at StdJDBCDelegateTest.java:119

org.quartz.impl.jdbcjobstore.StdJDBCDelegateTest > testSelectSimpleTriggerWithExceptionWithExtendedProps FAILED
    java.lang.NoClassDefFoundError at StdJDBCDelegateTest.java:90
        Caused by: java.lang.ExceptionInInitializerError at StdJDBCDelegateTest.java:119

org.quartz.impl.jdbcjobstore.StdJDBCDelegateTest > testSelectBlobTriggerWithNoBlobContent FAILED
    java.lang.NoClassDefFoundError at StdJDBCDelegateTest.java:73
        Caused by: java.lang.ExceptionInInitializerError at StdJDBCDelegateTest.java:119

org.quartz.impl.jdbcjobstore.StdJDBCDelegateTest > testSelectTriggerToAcquireHonorsMaxCount FAILED
    java.lang.NoClassDefFoundError at StdJDBCDelegateTest.java:145
        Caused by: java.lang.ExceptionInInitializerError at StdJDBCDelegateTest.java:119

org.quartz.impl.jdbcjobstore.UpdateLockRowSemaphoreTest > testSingleFailureFollowedBySuccessUsingUpdate FAILED
    java.lang.ExceptionInInitializerError at UpdateLockRowSemaphoreTest.java:35
        Caused by: java.lang.reflect.InaccessibleObjectException at UpdateLockRowSemaphoreTest.java:35

org.quartz.impl.jdbcjobstore.UpdateLockRowSemaphoreTest > testDoubleFailureFollowedBySuccessUsingUpdate FAILED
    java.lang.NoClassDefFoundError at Unsafe.java:-2
        Caused by: java.lang.ExceptionInInitializerError at UpdateLockRowSemaphoreTest.java:35

org.quartz.impl.jdbcjobstore.UpdateLockRowSemaphoreTest > testFallThroughToInsert FAILED
    java.lang.NoClassDefFoundError at Unsafe.java:-2
        Caused by: java.lang.ExceptionInInitializerError at UpdateLockRowSemaphoreTest.java:35

org.quartz.impl.jdbcjobstore.UpdateLockRowSemaphoreTest > testSingleSuccessUsingUpdate FAILED
    java.lang.NoClassDefFoundError at Unsafe.java:-2
        Caused by: java.lang.ExceptionInInitializerError at UpdateLockRowSemaphoreTest.java:35

319 tests completed, 8 failed, 1 skipped

> Task :quartz:test FAILED

FAILURE: Build failed with an exception.

[nmondal]

@melloware who would give us another approval?

[melloware]

cc @jhouserizer

I will admit it doesn't look like there has been much activity here which is dissapointing and last public release was 2019?

[jhouserizer]

There were releases made earlier in the year (with dozens of changes) as RCs awaiting feedback. Official non-RC releases will be made in the next week or two.

It's true that current efforts on the project are sporadic. This contribution is interesting and will be looked at .

[nmondal]

Added the DCO fix as expected by the doc.

[t-beckmann]

There are no releases, no feedback on PRs nor on issues, no replies on the user's list, and the developer's forum link points to nowhere. Quartz is not only poorly maintained, but it is not maintained at all...

[raduking]

I think a code format should be run on these so that the formatting is consistent. For example some methods have a space before open bracket some don't.

public void foo1() {
    // ...
}

and

public void foo2(){
    // ...
}

[t-beckmann]

These changes are not necessary, also typo here. Changes to build.gradle should be reverted.

[damingerdai]

i think this is better

  log.warn("{}{}", message, ex);

[jhouserizer]

Unfortunately, due to the change of ownership of this project, the terms of contribution have been updated, and this PR will need to be re-created, agreeing to the new terms.