Upgrade to the latest dependencies

* Upgrade to Gradle `7.6`
* Apply Spring Integration code style
* Replace obsolete Travis CI with GitHub Actions
* Fix test XML configs for the latest Mockito

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,25 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: 'status: waiting-for-triage, type: enhancement'
+assignees: ''
+
+---
+
+**Expected Behavior**
+
+<!--- Tell us how it should work -->
+
+**Current Behavior**
+
+<!--- Explain the difference from current behavior -->
+
+**Context**
+
+<!--- 
+How has this issue affected you?
+What are you trying to accomplish?
+What other alternatives have you considered?
+Are you aware of any workarounds?
+-->