Postal code mapping to municipalities

[DJSmallSquare]

I think there's room to improve the way one maps the postal codes to municipalities. There are two fixed values: (i) the official list of municipalities and (ii) the official list of postal codes. We should be able to figure out a way to map one postal code to exactly one municipality. However, a municipality may have multiple postal codes.
I found an Excel file detailing the correspondence between postal codes and municipalities. It is dated as of 2016.01.01. Therefore, we know we should end up with exactly 2294 municipalities after completing the mapping procedure. According to the same file, there are 3186 postal codes. Therefore, we should end up with a object containing 3186 rows, where each postal code is match with exactly one municipality.
The challenge here is that postal codes may overlap one or more municipalities. A trade-off will be necessary.