Function validatePartyId

validatePartyId(value: string): PartyIdError | undefined
Checks the shape of a party id: a non-blank hint, the :: separator, and a 68-character hex fingerprint. Returns undefined when nothing is wrong. Shape only — whether the party exists is the ledger's answer, not this function's.

Reach for this over isValidPartyId when the caller needs to say what went wrong.
Parameters
- value: string
Returns PartyIdError | undefined
Example
```
validatePartyId('nico:1220df94') // 'missing-separator'
validatePartyId('nico::1220df94') // 'invalid-fingerprint': 8 hex characters, not 68
```
- Defined in canton-dappbooster/src/utils/partyId.ts:36