Make form to submit via post instead of get

[Lubosky]

📝 A short description of the changes

When creating new application, originally the form was submitted via get method. In terms of validation we were relying on HTML5 built-in validations however the styles did not match the rest of the app. This changes that and form is now submitted via post method (error styles match rest of the application).

🔗 Link to the relevant story (or stories)

Asana card here: https://app.asana.com/0/1200504523179345/1207640920856071/f

Deployment implications

None

✅ Checklist

• Features that cannot go live are behind a feature flag/env var or specify deploy date and open PR as draft
• I have checked that commit messages make sense and explain the reasoning for each change
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have squashed any unnecessary or part-finished commits

🖼️ Screenshots (if appropriate - no PII/Prod data):