New studies & tests logic

backend/app/models/__init__.py

 from sqlalchemy import (
+    JSON,
     Column,
     Float,
     Integer,
@@ -43,7 +44,7 @@ class User(Base):
     password = Column(String)
     type = Column(Integer, default=UserType.STUDENT.value)
     is_active = Column(Boolean, default=True)
-    availability = Column(String, default=0)
+    bio = Column(String, default="")
     ui_language = Column(String, default="fr")
     home_language = Column(String, default="en")
     target_language = Column(String, default="fr")
@@ -51,6 +52,10 @@ class User(Base):
     gender = Column(String, default=None)
     calcom_link = Column(String, default="")
     last_survey = Column(DateTime, default=None)
+    availabilities = Column(JSON, default=[])
+    tutor_list = Column(JSON, default=[])
+    my_tutor = Column(String, default="")
+    my_slots = Column(JSON, default=[])
 
     sessions = relationship(
         "Session", secondary="user_sessions", back_populates="users"