Improve InvalidSchema exception by adding specific fields that do not match

[artemrys]

I am talking about this InvalidSchema exception.

It may be useful to show at most 3 (for example) fields that have different types. It should help to debug a type mismatch faster.

[tswast]

Great suggestion. I think we do a "set difference" in order to discover schema mismatch, so this should be possible to figure out and include in the exception.

[artemrys]

Great, I will start working on it then.

[tswast]

I'm a bit wary of including this information in the actual exception message due to potential privacy issues around logging. Instead, I'm adding local_schema and remote_schema properties to InvalidSchema in #449

[tswast]

So long as we leave out description (and other column metadata like IAM roles), which can contain arbitrary text (possibly, though unlikely to be PII) I do think it would be an improved experience if the string representation of InvalidSchema showed the diff of field names and the types.