technical user

[sergimicoortiz]

• [x] Enum user types
• [x] Change technical guard
• [x] This user can put bikes to maintenance
• [x] This user can put slots to maintenance
• [x] Create a pege for this user to change the bike status
• [x] Create a pege for this user to change the slot status
• [x] qr generator for bikes and slots gql for now. Only the maintenance and admin users can do this
• [x] The qr have an url to that specific bike/slot