Add hasOne relation type to `lb4 relation`

[dhmlau]

Description / Steps to reproduce / Feature proposal

Trying out the lb4 relation command from the master branch and realized that there are only 2 model relation types available for selection: belongsTo and hasMany.

We should add the hasOne relation type as one of the options as well.

Acceptance Criteria

• when running lb4 relation command, there should be 3 options for relation types: belongsTo, hasMany and hasOne (should be added in this work item) ( should implement the "inclusion resolver" prompt too)
• add related cli tests

[dhmlau]

@lakinmohapatra, this is the same issue you've reported. Would you like to submit a PR? Thanks.

[lokeshmohanty]

@dhmlau I would like to work on this. Can you assign this to me?

[dhmlau]

@lokesh1197, of course!

[dhmlau]

@lokesh1197, are you still interested in working on a PR for this? I think I haven't seen a related PR. Thanks.