Add duration utils (#3700)

* Add duration utils

* Bump changelog and version

* Bump changelog and version

---------

Co-authored-by: Robert <[email protected]>

Author: RobertRuf

CHANGELOG.md

@@ -1,4 +1,6 @@
 ## Release (2025-xx-xx)
+- `core`: [v0.18.0](core/CHANGELOG.md#v0180)
+  - **New:** Added duration utils
 - `stackitmarketplace`: [v1.16.0](services/stackitmarketplace/CHANGELOG.md#v1160)
   - **Breaking Change:** Remove unused `ProjectId` model struct 
 - `iaas`: [v1.1.0](services/iaas/CHANGELOG.md#v110)

core/CHANGELOG.md

@@ -1,3 +1,6 @@
+## v0.18.0
+- **New:** Added duration utils
+
 ## v0.17.3 
 - **Dependencies:** Bump `github.com/golang-jwt/jwt/v5` from `v5.2.2` to `v5.2.3`
 

core/VERSION

@@ -1 +1 @@
-v0.17.3
+v0.18.0