Missing error code for some error messages

Some of the errors are missing error code. We will need to have the error code in order to handle the localization of messages that are displayed in error log. Also this will simplify the any changes to the error verbiage.

Approach

• Move all messages which are not used in logger to https://github.com/folio-org/mod-data-export/blob/master/src/main/java/org/folio/util/ErrorCode.java class
• Change Error log service(https://github.com/folio-org/mod-data-export/blob/master/src/main/java/org/folio/service/logs/ErrorLogService.java#L53) to take Errorcode as parameter than a String to enforce this rule is followed even for future changes
• Add error code to errorLogs schema
• We also need a way to be able to send values For example: If the message is "5 instances not found, and 13 holdings have incorrect mapping" We need to be able to send needed mappings in a proper way

Expected behavior:
All data export backend error messages have associated error code