Applying mapping profile - Combination of record types - selected fields - missing transformation

Purpose
This story addresses exporting multiple record types when the user wants to export only selected fields and each field but does not provide transformation.

Scenario 1:
Given: the mapping profile contains selected fields from the inventory instance and the fields don't have specified transformations
When: the fields have mappings in rules.json (used for generating records on the fly)
Then:

1. Only fields selected in the mapping profile are part of the exported record
2. The fields are populated with the data coming inventory instance record according the existing mapping rules
3. LDR is re-generated based on the selected fields
4. .mrc file is generated
5. Unit and API tests are written

Scenario 2:
Given: the mapping profile contains selected fields from the inventory instance and the fields don't have specified transformations
When: the fields have don't have mappings in rules.json (used for generating records on the fly)
Then:

1. the fields are being disregarded during the export
2. the log is populated with the information that the transformation was not available
3. .mrc file is generated and populated only with the fields that have transformations or mappings available

Scenario 3:
Given: the mapping profile contains selected fields from holdings or items records
When: and the fields don't have specified transformations
Then:

1. the fields are being disregarded during the export
2. the log is populated with the information that the transformation was not available
3. .mrc file is generated and populated only with the fields that have transformations or mappings available