feat(DTFS2-7300): update db on effective from date page

[BethThomas141]

Introduction :pencil2:

The effective from date page should update the database when a user presses 'continue'. It should also display previously entered values (e.g. if they press back)

I've followed the implementation precedent set on the deal cancellation reason page and bank request date page for consistency.

Resolution :heavy_check_mark:

• get effective from date from the database
• update effective from date
• validate deal exists & submission type is valid on both post and get endpoints

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
11.6% Duplication on New Code

See analysis details on SonarCloud