Student: FE: Real time error handling around Course Information feature

**User Story**
As a _student user_, **I want** to receive a real time user friendly error message when I enter invalid data **so that** I can correct my mistake before I continue with the application

**Acceptance Criteria**
- [ ] Error message is displayed (TBD content) when a student enters identical course information
- [ ] Error message is displayed (TBD content) or a message is displayed (TBD content) when they can no longer add more courses to this section.
- [ ] Error message is displayed (TBD content) when the course start date/end date in the course information section does not match the offering dates in the "The program I will be attending" dropdown list

**Business context**
- The course information does not have any impact on the student's assessment
- COE - the institution cannot view the course information that the student entered Ref #3395
- PIR - the institution can view the course information that the student entered

Ref. MODInbox email

No files or tests are named. Start by locating the frontend Course Information feature and tracing where course entries and offering dates are validated. Done means the three invalid-input cases display agreed user-friendly real-time messages, with the final wording and validation limits resolved first.

Written by the indexing model from the issue text.