[re #12345] Created JiraRestClient service for easier and more clean data fetching
- Created separate service for fetching data via library from Jira API
- This service is gonna be used (most likely) in other pumps as well
- It separates logic (fetching logic should not be in the "general" services) and the code is also much more clean and readable (especially in the services)
- Also fixed a couple of issues reported by PMD or @jpvlck (ty John Pork!)