Bug: Prevent saving multiple locations with the exact same name in our database

[positiveimpact]

Describe the bug
Some location names such as "Potsdam, Germany" or "Erlangen, Germany" are stored multiple times as seperate entities in our database. This likely roots in the data structure of open streetmaps. In most instances the redundant location will all have the same osm_id but differing place_ids.

Examples
For the location Potsdam, Germany there are at least three different locations which all have the osm_id 62369 but different place_ids ( 297654326, 297994811, 307691326)

These locations should be merged and in the future only one entry per location should be created, potentially using the osm_id as a unique identifier. But to make this decision we'll have to investigate the different between osm_id and place_id further.