feat: throw error if duplicate map

[jef]

Closes #245

• Tries to find if the hash of the .bsp is in the database. If it is, then it throws a ConflictException.

Screenshots (if applicable)

Checks

• !! DONT IGNORE ME !! I have ran nx run db:create-migration <name> and committed the migration if I've made DB schema changes
• I have included/updated tests where applicable (see Testing)
• I have followed semantic commit messages e.g. feat: Add foo, chore: Update bar, etc...
• My branch has a clear history of changes that can be easy to follow when being reviewed commit-by-commit
• My branch is functionally complete; the only changes to be done will be those potentially requested in code review
• All changes requested in review have been fixuped into my original commits

[tsa96]

Thanks for first contribution! This check makes sense, though prefer .exists (see comments). Though we actually have two different endpoints that handle BSP uploads, the initial submission, and updated versions after then. So you need a check in MapsService.submitMapVersion as well, and E2E tests there as well.

The Volta thing I'm okay with, I'd been meaning to get round to pinning an Node version at some point anyway. Personally I'm using NVM but fine with switching.

[tsa96]

Something weird's happened with Git here - if you need a hand just ping me on Discord in #website!