[FIX] Creating multiple plugin instances

[kristian]

Recent changes in commit 762cde2 caused that always the same UI5 middleware was returned, even for multiple KarmaServer instances. Karma however, initializes the plugins for each KarmaServer instance, which causes the same middleware to be added twice to the sub-router introduced in the mentioned commit. All in all this causes unexpected behaviour in tests, e.g. failing requests when sending PATCH requests.

[matz3]

Thanks! I think the plugin wasn't really capable of being initialized multiple times and it only worked by chance.

I've added a test and updated the implementation a bit.
Still, the tests need to be extended to ensure that a new framework instance is created every time. I'll try to finish that in the next days.

[coveralls]

Coverage increased (+1.4%) to 53.141% when pulling d2200d5 on kristian:master into 6fb7e68 on SAP:master.

[matz3]

@kristian again, thanks for this PR 👍🏻 It's released with v2.3.2

[kristian]

@matz3 Most welcome :)