Simplify layer customization logic for both Maven and Gradle and
refactor some internals of the Gradle plugin.
Both Maven and Gradle now use a simpler customization format that
consists of `application`, `dependencies` and `layer order` sections.
The `application`, `dependencies` configurations support one or more
`into` blocks that are used to select content for a specific layer.
Closes gh-20526
This commit provides a versioned xsd for the layers configuration of the
Maven plugin. The version starts at `2.3` to match with the Spring Boot
feature release in which this was introduced.
Closes gh-20663
This commit adds an additional 'layers/configuration' property that can
be used to refer to a separate layers configuration file. This separate
file defines:
* The layers and their order of precedence,
* How libraries are handled using filters that match against the
coordinates of each library, and
* How classes are handled using filters that match against the location
of the entry
An XSD to validate the XML configuration file is available.
Closes gh-20295
Co-authored-by: Stephane Nicoll <snicoll@pivotal.io>
