Infrastructure import problems related to umlauts

[MartinWahnschaffe]

Bug Description

1. Importing ü, ä, ö, etc. does not correctly work (e.g. misspelled in name) sormas_import_region_germany.txt
2. Importing a district for a region with a ß in it's name does not work. The logic does an uppercase and this probably behaves differently for Java and JPA/SQL.. sormas_import_district_landkreise.txt

TODO

• [x] Write unit test
• [x] Fix umlaut encoding problems
• [x] Fix ß uppercase problem
• [x] ~Accept import files that come with a BOM~ => using BOM is generally not recommended by Unicode
• [x] Add comments to CaseImporter and InfrastructureImporter to explain what happens

[MateStrysewske]

I've created some unit tests. Unfortunately, H2 seems to behave differently than PostgreSQL which is why all tests are passing right now.

We could solve the ß <-> SS problem by using toLowerCase instead of toUpperCase and maybe adding two different areas of name matching (1. match for exact name without manipulating the string, 2. use toLowerCase).