Config missing needed values

[Jday7879]

Values needed in append_back_data need to be added to config
"back_data_type"
"imputation_marker_col"

[AntonZogk]

@Jday7879 for the testing i had added this https://github.com/ONSdigital/monthly-business-survey-results/blob/main/tests/data/staging/back_data/test_config.json , this because the config isn't integrated in the package yet .

In the config we need to define these for append_back_data function:

"back_data_type":"type",
"imputation_marker_col":"imputation_marker"

Essentially these are used to link the imputation marker column name from our methods with imputation type from csw relevant column.

[Jday7879]

Thanks @AntonZogk I've got a branch which has some small fixes to run the full pipeline, I'll add it there :)