Get a new unique identifier for Person model

[leportella]

Since 'unique' fields are complicated to gather. A combination of name-birthday could be considered a "good enough" unique field for our dataset. since this could be a sensitive information, we can transform this slug into a hash.

This would facilitate working with difficult databases and use a lot of information that are not
rightly gathered by some sources.

[cuducos]

Outdated after #88