chore: add missing security file and pull request template (#1)

Author: marceljk

.github/pull_request_template.md

@@ -0,0 +1,22 @@
+## Description
+
+<!-- **Please link some issue here describing what you are trying to achieve.**
+
+In case there is no issue present for your PR, please consider creating one.
+At least please give us some description what you are trying to achieve and why your change is needed. -->
+
+relates to #1234
+
+## Checklist
+
+- [ ] Issue was linked above
+- [ ] **No generated code was adjusted manually**
+- [ ] Changelogs
+    - [ ] Changelog in the root directory was adjusted
+    - [ ] Changelog(s) of the service(s) were adjusted
+- [ ] VERSION file(s) of the service(s) were adjusted
+- [ ] Code format was applied: `make fmt`
+- [ ] Examples were added / adjusted (see `examples/` directory)
+- [ ] Unit tests got implemented or updated
+- [x] Unit tests are passing: `make test` (will be checked by CI)
+- [x] No linter issues: `make lint` (will be checked by CI)  

SECURITY.md

@@ -0,0 +1,9 @@
+# Reporting Security Issues
+
+**Please do not report security vulnerabilities through public GitHub issues.**
+
+We at STACKIT take security seriously. We appreciate your efforts to responsibly disclose your findings, and will make every effort to acknowledge your contributions.
+
+To report a security issue, please send an email to [stackit-security@stackit.de](mailto:stackit-security@stackit.de).
+
+Our team will send a response indicating the next steps in handling your report. After the initial reply to your report, the security team will keep you informed of the progress towards a fix and full announcement, and may ask for additional information or guidance.