[iOS] Full screen loader whille course is upgarding

[moiz994]

While implementing IAP on the legacy apps, it was seen that after processing the payments it takes some time for the course to upgrade. Considering design heuristics and for a more interactive approach, we have implemented a full-screen loader to show while the learners wait for their course to be upgraded.

Acceptance criteria:

• The loader shows up after the payment is processed and the backend is unlocking the course content
• The loader is not shown when upgrading is completed
• The loader illustration should either be generic or should go with the theme of the app

Current implementation:
Video Demo