Add bindings command-line option for build-image goal

[TYsewyn]

• Allowed volume bind mounts to be supplied through the spring-boot.build-image.bindings and --bindings properties
• Added command-line bindings to those configured in pom.xml or the Gradle build script, taking precedence over a configured one when they share the same container destination path

[snicoll]

@TYsewyn thanks for the PR. On the the top of my head, I am not aware of a commad lline option that would be additive. In Maven, in particular, this feels like an anti-pattern to me. If you provide a property on the command line, its purpose is to override the default. If you really want to add, then the method should be named differenty but it's a bit at odd with maven again.

Can you review the above and clarify the intent?

[TYsewyn]

Thanks for the review, @snicoll! The intent is to add more, or override, Buildpacks bindings from the CLI.
Some of the bindings in our CI environment are dynamic and we can't define them in our Maven or Gradle configuration.
As an alternative we could change --bindings to take precedence over what has been configured, and add --add-binding (repeatable) to be additive to what's already configured in the build scripts. The additional binding passed as CLI argument would then take precedence over what's already defined.

For Maven I'd then split this into spring-boot.build-image.bindings (the full override) and spring-boot.build-image.additional-bindings (the additions, comma separated, taking precedence over what's defined in pom.xml)

[snicoll]

Some of the bindings in our CI environment are dynamic and we can't define them in our Maven or Gradle configuration.

You don't need an additional property for that, do you? If you expose the original property, you can then manipulate any way you like in your project. I am not keen to have a addBindings feature and/or property for that reason. Can you amend your PR to expose the property?