Function isCmcdCustomKey

isCmcdCustomKey(key: CmcdKey): boolean
Check if a key is a valid custom key: a lowercase first letter, then characters from a-z 0-9 . -, with a hyphen that is neither the first nor the last character. These are the CTA-5004-B custom-key rules restricted to names that survive RFC 8941 key serialization.
Parameters
- key: CmcdKey
  The key to check.
Returns boolean
true if the key is a custom key, false otherwise.
Example
```
equal(isCmcdCustomKey('com.example-key'), true)
equal(isCmcdCustomKey('br'), false)
```
- Defined in isCmcdCustomKey.ts:22