Docs: Update Installation Guide for JDK7 (JBOSS5/SIGTRAN) users.

[delvatt]

Is this a BUG REPORT or FEATURE REQUEST?:

/kind bug

What happened:
As of june 18th 2018, Sonatype no longer supports TLSv1.1 and below, which is the default TLS supported in JDK7 versions before 1.7.0_131-b31. see the original blogpost

Thus, running mvn clean install as suggested in the documentation for building form source will generate the following error: (see attached file for more)

org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356) Caused by: javax.net.ssl.SSLException: Received fatal alert: protocol_version

resulting in a build faillure.

Possible options to fix this unwanted behavior is to update the installation guide to specify the configuration of the Java runtime to enable TLS 1.2 by adding -Dhttps.protocols=TLSv1.2, just as:

mvn clean install -Dhttps.protocols=TLSv1.2

What you expected to happen:
mvn clean install should have resulting in a successful build, assuming every installation prerequisites were fulfilled.

How to reproduce it (as minimally and precisely as possible):
Assuming your are running the last public JDK7 release (build 1.7.0_80-b15), or any paying support version below 1.7.0_131-b31 with no cached dependency packages in your local maven repository:

• Follow the instructions in the installation guide for building from source.

Anything else we need to know?:
This is not an issue with the USSD GW itself, but more of a documentation issue, and the immediate value by updating the documentation will be in saving time of every new user trying to build the GW from source for the first time.

Affected users are those who are trying to build the GW with JDK7 for JBOSS5/SIGTRAN support. The affected JDK versions are public releases up to 1.7.0_80-b15 and paying support versions before 1.7.0_131-b31. These versions of JDK rely by defaut on TLSv1.1 which is no longer supported by Central.
Users of JDK 1.7.0_131-b31 and above including Java 8 are not affected.