Remove the deprecated method substr from application

**Describe the task**
Substr is a deprecated method which needs to be removed across the application.
Note: As this method is widely used at file integration to parse the record data, make sure that the replacement of substr exactly replaces the logic what substr does. The OOTB method subString is not exactly the replacement of substr.

**Acceptance Criteria**
- [ ] Replace all substr with an equivalent method.

**Additional context**
- Add any other context about the task here.
- Or here

Search the application for uses of the deprecated substr method, then inspect the file-integration parsing paths first. Compare each candidate replacement with substr's behavior rather than assuming subString is equivalent. Done means all uses have an equivalent replacement and the record-data parsing logic remains unchanged.

Written by the indexing model from the issue text.