ruta-core is unable to access extension from ruta-core-ext in OSGI context

[reckart]

Describe the bug
ruta-core-ext contains some extension functions that need to be enabled e.g. as

createEngineDescription(
    RutaEngine.class,
    RutaEngine.PARAM_ADDITIONAL_EXTENSIONS, StringOperationsExtension.class);

However, the ruta-core bundle has no optional import of the required packages from ruta-core-ext and there is also no alternative such as an SPI which would allow discovery.

To Reproduce
Steps to reproduce the behavior:

1. Try running a Ruta engine which uses an extension in an OSGI context

Expected behavior
The simplest solution would probably be adding an optional import for the packages of ruta-core-ext to the ruta-core bundle.

Please complete the following information:

• Version: 3.3.0