Avoid from overriding the Dtag accidentally

[dadamu]

Feature description

Currently, updating the Dtag does not confirm the user's willing once. It might let users override it accidentally.
Adding a flag IsUpdateDtag to confirm if the user want to update the dtag maybe useful to avoid the situation mentioned above.

Implementation proposal

Add is_update_dtag field into MsgSaveProfile proto struct.

message MsgSaveProfile {
  string dtag = 1;

  string nickname = 2;

  string bio = 3];

  string profile_picture = 4;

  string cover_picture = 5;

  string creator = 6;

  bool is_update_dtag = 7;
}

[RiccardoM]

Personally, I think that instead of adding a new field, we can change how the MsgSaveProfile works by making the DTag optional and then:

1. if the user does not yet have a profile and the DTag is not specified, an error is returned
2. if the user does have a profile and the DTag is not specified, the old DTag is preserved
3. if the user does have a profile and the DTag is specified, the new DTag will replace the old one

This would also require the CLI command to be updated by having 0 required arguments and make the DTag an optional flag instead.

Please @bragaz let me know what you think as well

[leobragaz]

@RiccardoM I would prepend for this solution instead adding an extra field to the msg.
The implementation should be easy to handle since it's pretty much similar to how we handle the other CLI command fields.
I think we should write an ADR anyway to track the changes. If you want, I can proceed to draft it and later, to implement it if passed.

[RiccardoM]

@bragaz Ok, you can go ahead with the ADR