Added new class Shelter

[LordDangerous]

New class Shelter

[jorgechp]

Great! just take into consideration that is better to use Long instead of String when dealing with identifiers (the user is an exception in our case)

[PauMAVA]

@jorgechp Bump. I need this to implement the relations form Pet to Shelter.

[elskater98]

Hello @LordDangerous @PauMAVA, You should add more validations for mobile field.

Examples: +3466666AA66,empty string.

In this case, you should use regex. https://stackoverflow.com/questions/10631960/validate-mobile-number-using-hibernate-annotation

[elskater98]

Well done!