Omalkja/url shortener

I have initially pulled the latest state from develop branch. Then I added in chunks the code related to:

1. URL tree logic
2. Process URL config
3. Update URL by rewriting Bookmark Service
4. Error handling + adapting/adding tests.

In total there are 52 tests.

requested review from @paul.pestov

assigned to @malkja

@paul.pestov It says that 4 commits and 1 merge commit will be added to develop. Do you know why 1 merge commit as well ?

added 1 commit

• c57cf355 - style: If else curly braces

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added 1 commit

• 85cf37bd - refactor: Bookmark Service

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