fix(RocketChatClientCallBuilder): fix proxy access without credentials (JENKINS-55890)

[famod]

Including refactoring to improve code quality
and to reduce complexity of different execution paths.

Also fixes:
org.apache.http.conn.UnsupportedSchemeException: http protocol is not supported
when using proxy (with or without auth) and trustSSL is active.

Also switches from deprecated SSLSocketFactory to SSLConnectionSocketFactory.

https://issues.jenkins-ci.org/browse/JENKINS-55890

[famod]

Please note that I did not create new tests because I did not introduce new features.
Nevertheless, test coverage in this area should be improved - especially regarding proxy handling!

PS: Credits to my colleague @uhanisch whom I worked with on this issue.

[hypery2k]

thanks for the PR, but actually the integration test is failing. Will try to find time next week to check

[famod]

The failures on travis don't seem related to my actual code changes:

[ERROR] jenkins.plugins.rocketchatnotifier.rocket.RocketChatClientCallBuilderIT  Time elapsed: 0.36 s  <<< ERROR!
java.lang.NoSuchMethodError: org.junit.rules.Timeout.seconds(J)Lorg/junit/rules/Timeout;
	at org.jvnet.hudson.test.JenkinsRule.apply(JenkinsRule.java:579)
	at org.junit.rules.RunRules.applyAll(RunRules.java:24)
	at org.junit.rules.RunRules.<init>(RunRules.java:13)
	at org.junit.runners.BlockJUnit4ClassRunner.withTestRules(BlockJUnit4ClassRunner.java:376)
	at org.junit.runners.BlockJUnit4ClassRunner.withRules(BlockJUnit4ClassRunner.java:331)
	at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:248)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
	at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:365)
	at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:273)
	at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:238)
	at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:159)
	at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:384)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:345)
	at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:126)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:418)

[hypery2k]

thanks for the PR, I'll check for the test errors

[famod]

@hypery2k thanks for merging! In case I find the time for this: What would be right approach for this project/plugin to test proxy access? Something docker-based? Or just a java proxy implementation that is embedded into the unit/integration test like https://github.com/adamfisk/LittleProxy?

[hypery2k]

I like the Java based integration test approach. Feel free to send a PR. Any help is appreciated