Add Option to disable SSL verification

[HelvetiaAppDev]

We are behind a corporate firewall proxy, that decrypts and encrypts every traffic. Despite having the root certificate registered in Java, this library fails to connect to github.

Caused by: javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
	at java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:578)
	at java.net.http/jdk.internal.net.http.HttpClientFacade.send(HttpClientFacade.java:123)
	at org.kohsuke.github.extras.HttpClientGitHubConnector.send(HttpClientGitHubConnector.java:72)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:431)
	... 6 more
Caused by: javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
	at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:131)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:371)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:314)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:309)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.checkServerCerts(CertificateMessage.java:1357)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.onConsumeCertificate(CertificateMessage.java:1232)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.consume(CertificateMessage.java:1175)
	at java.base/sun.security.ssl.SSLHandshake.consume(SSLHandshake.java:396)
	at java.base/sun.security.ssl.HandshakeContext.dispatch(HandshakeContext.java:480)
	at java.base/sun.security.ssl.SSLEngineImpl$DelegatedTask$DelegatedAction.run(SSLEngineImpl.java:1277)
	at java.base/sun.security.ssl.SSLEngineImpl$DelegatedTask$DelegatedAction.run(SSLEngineImpl.java:1264)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:712)
	at java.base/sun.security.ssl.SSLEngineImpl$DelegatedTask.run(SSLEngineImpl.java:1209)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.net.http/jdk.internal.net.http.common.SSLFlowDelegate.lambda$executeTasks$3(SSLFlowDelegate.java:1118)
	at java.net.http/jdk.internal.net.http.HttpClientImpl$DelegatingExecutor.execute(HttpClientImpl.java:157)
	at java.net.http/jdk.internal.net.http.common.SSLFlowDelegate.executeTasks(SSLFlowDelegate.java:1113)
	at java.net.http/jdk.internal.net.http.common.SSLFlowDelegate.doHandshake(SSLFlowDelegate.java:1079)
	at java.net.http/jdk.internal.net.http.common.SSLFlowDelegate$Reader.processData(SSLFlowDelegate.java:484)
	at java.net.http/jdk.internal.net.http.common.SSLFlowDelegate$Reader$ReaderDownstreamPusher.run(SSLFlowDelegate.java:268)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$LockingRestartableTask.run(SequentialScheduler.java:205)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$CompleteRestartableTask.run(SequentialScheduler.java:149)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$SchedulableTask.run(SequentialScheduler.java:230)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
	at java.base/sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:439)
	at java.base/sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:306)
	at java.base/sun.security.validator.Validator.validate(Validator.java:264)
	at java.base/sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:285)
	at java.base/sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:144)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.checkServerCerts(CertificateMessage.java:1335)
	... 21 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
	at java.base/sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:141)
	at java.base/sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:126)
	at java.base/java.security.cert.CertPathBuilder.build(CertPathBuilder.java:297)
	at java.base/sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:434)
	... 26 more

Our current Solution is to provide a custom connector that ignores all checks, but as setConnector is deprecated it would be appreciated, if there was some option to do this e.g. disableSSLVerification.

[bitwiseman]

Switch to GitHubConnector.

This library tries to be agnostic as to connection, but you are welcome to submit enhancements to the extras.