at_commons changes for update verb isEncrypted

[murali-shris]

Is your feature request related to a problem? Please describe.

Ability for a client to set isEncrypted = false in update verb.
Client can either decide not to encrypt the value or use their own encryption algorithm.

Describe the solution you'd like

• Modify toAtProtocolFragment in AtKey-->Metadata to set isEncrypted (true or false)
• Point to the changes and run tests.
• Document code changes required in at_client/at_lookup and at_server

Describe alternatives you've considered

No response

Additional context

No response

[murali-shris]

#669