Implement edition of JSON flat file

[JosePizarro3]

For now, assume that schema is a simple, flat dictionary, the same structure you get when calling to_json() on a Pydantic BaseModel with a few fields and no nested structure. The only edits we need at this stage are:

1. changing the data type of existing fields
2. adding new fields

And some extra considerations:

• A minimal frontend is optional. The essential part is getting the FastAPI - MongoDB connection working reliably. If you want to experiment with a small frontend, feel free, but it’s not required.
• This implementation will probably require creating an initial schema (even an empty one is fine).
• We do not need import/export features yet.
• We also do not need to handle nested or more complex schemas at this point.

[KoeppelSoftwareEngineer]

I think I implemented everything. But now the code is not easy and simple to read. For the beginning to complex?