chores(x2a): refactor router for better maintainability (redhat-developer#2293)

* chores(x2a): refactor router for better maintainability

Signed-off-by: Marek Libra <marek.libra@gmail.com>

* refactor router tests and increase coverage

Signed-off-by: Marek Libra <marek.libra@gmail.com>

* Fix tests

---------

Signed-off-by: Marek Libra <marek.libra@gmail.com>

Author: mareklibra

workspaces/x2a/.changeset/smooth-hotels-tell.md

@@ -0,0 +1,5 @@
+---
+'@red-hat-developer-hub/backstage-plugin-x2a-backend': patch
+---
+
+Refactor router for better maintainability - split to multiple files.