Analysis: Single student enters themself as dependant (question needs validation)

Add warning message (or some other mechanism) to prevent a student from entering themselves as a dependant

**Acceptance Criteria**
- [ ] [TBD]

**Additional context**
- e.g. Pop up in red to warn the student that they have entered themselves as a dependant or some other mechanism to prevent them from getting extra funding
- PSI request

No file, test, or entry point is named. First validate the PSI request and inspect the student dependant-entry flow to determine how self-entry is detected and whether a warning or prevention mechanism is required; define concrete acceptance criteria before implementation, with done meaning a student cannot obtain extra funding by entering themself as a dependant.

Written by the indexing model from the issue text.