Newborn Pro-Rate

**Current Behaviour:**
- Student can submit Request a Change and Add a dependant at any time. If this is approved, the new dependant is incorporated into the assessment as of the original study star date, i.e. the student will receive funding for that dependent for the entire study period.

**Expected Behaviour:**
- If student submits a Request a Change for a new dependant, whose birthday falls within the study period, then the student should only be eligible for funding for that student starting at their birthday (as oppose dot the study start date, before they were born).
- Camunda logic needs to handle these dependants seperately, and assess funding that is proportional to the portion of the study period in which the new child was alive (i.e. "Pro-rate")

**Context:**
As an interim solution after Part-Time launches, it was determined that these dependants would simply receive funding for the entirety of the study period.

Start by locating the Camunda logic that handles Request a Change submissions and dependant assessment. Trace how a dependant's birthday and the study period currently determine funding eligibility. Done means a dependant born during the study period receives funding only from their birthday, with the assessment prorated for the time they were alive.

Written by the indexing model from the issue text.