Issue #5019 - hot-reload SSL certificates if keystore file changed

[lachlan-roberts]

Issue #5019

Added an ssl-reload module which uses Scanner to monitor the keystore file registered with the SslContextFactory and reloads the keystore file if it detects any changes.

[sbordet]

@lachlan-roberts please redo this PR as follows:

• remove the Maven module jetty-ssl-reload as it is only 1 class
• move the Jetty module jetty-ssl-reload.mod to Maven module jetty-server, where the other SSL Jetty modules are
• class and test cases should be in jetty-util.
• add a test where the keyStore file is a symlink and change the target of the symlink

[sbordet]

See PR comment.

[lachlan-roberts]

• remove the Maven module jetty-ssl-reload as it is only 1 class
• move the Jetty module jetty-ssl-reload.mod to Maven module jetty-server, where the other SSL Jetty modules are
• class and test cases should be in jetty-util.
• add a test where the keyStore file is a symlink and change the target of the symlink

@sbordet I did all these, but moved the tests to test-integration as it needed a Server dependency. Maybe there is a better location for this.

[joakime]

Some small changes.

[sbordet]

Please add some documentation in configuring-ssl.adoc.

[sbordet]

Please add *.adoc documentation as well.

[mantryashutosh]

Does the hot reload work if the keystore file is a soft link ?

[joakime]

I wouldn't expect it to, as the soft link itself wasn't updated, meaning there's no file change (last modified) detectable.

[lachlan-roberts]

@mantryashutosh it should still work if the keystore file is a soft link, we even have a test for this at KeyStoreScannerTest.testReloadChangingTargetOfSymbolicLink().

[mantryashutosh]

that's great, thank you so much @lachlan-roberts . Will test it out