[Document] : Document key can be created with invalid characters

Steps to reproduce

1. Created a 1 node kv cluster
2. Created a bucket 
3. Created a document with key = ab:cd

According to https://docs.couchbase.com/server/current/learn/data/data.html#keys

Special characters, such as (, %, /, ", and _, are acceptable.

Document key with ":" should not be allowed