Provide Liberty-aware UI assistance for setting Liberty config via Maven properties on Run/Debug config

[scottkurz]

As noted in https://github.com/OpenLiberty/ci.maven/blob/main/docs/common-server-parameters.md#setting-liberty-configuration-with-maven-project-properties one can use -Dliberty.var.abc=123 to cause LMP to generate a config dropin with a server config var named 'abc' set with a value of '123'. You can also set default vars, server.env entries, jvm.options, bootstrap.properties in analogous ways.

It could be nice for the feature UI to assist with this.

E.g. if we look at the m2e Run Config UI:

adding a parameter opens up a mini-wizard which offers the ability to access Eclipse workspace variables.

We could imagine a mini-wizard that offers a choice of property types: var, dflt vars, bootstrap.properties, etc. and generates the "liberty.var." part for you if you just type in the "suffix" of 'abc'.

EXTRA CREDIT

We could also imagine another layer of awareness where we actually look at variable/property references and suggest this set of strings as choices for the parameter "name". E.g. if there is a server.xml reference value=${abc} we might offer a choice of "abc" as the parameter name in the mini-wizard sketched out in the above design.