Add OSGI metadata to the JAR

[elharo]

The Cloud Tools for Eclipse team https://github.com/GoogleCloudPlatform/gcloud-eclipse-tools would like to add OSGI metadata to the final jar file. This will enable us to pull in this dependency from Maven Central rather than copying the binary file into our source tree. This will also assist any other developer who wants to reference this library from an Eclipse plug-in or another OSGI application.

This should have minimal impact on anyone not using OSGI. That is, it's just some extra entries in MANIFEST.MF everyone else will ignore. E.g.

Bundle-ManifestVersion: 2
Bundle-SymbolicName: com.google.api-java-client
Bundle-Version: 1.2.3
Export-Package: com.google.api-java-client;version="1.2.3"

(That's just an example, not an actual working patch.)
See http://blog.osgi.org/2013/01/get-help-adding-osgi-metadata-to-your.html

If you're amenable to this, I'll send a real patch.

[mattwhisenhunt]

Fixed by #1094

[elharo]

#1094 doesn't seem to have worked. Possibly we need to add it to each jar individually?

$ more META-INF/MANIFEST.MF
Manifest-Version: 1.0
Implementation-Title: GSON extensions to the Google APIs Client Librar
y for Java
Implementation-Version: 1.28.0
Built-By: root
Implementation-Vendor-Id: com.google.api-client
Created-By: Apache Maven 3.5.4
Build-Jdk: 1.8.0_181
Implementation-URL: https://github.com/google/google-api-java-client/g
oogle-api-client-gson
Implementation-Vendor: Google