Add Node.NAME_MAXLEN constant

gargantext/models/nodes.py

@@ -51,6 +51,8 @@ class Node(ValidatorMixin, Base):
     >>> session.query(UserNode).filter_by(typename='USER').delete() # doctest: +SKIP
     # Right: only user nodes are deleted.
     """
+    NAME_MAXLEN = 255
+
     __tablename__ = 'nodes'
     __table_args__ = (
             Index('nodes_user_id_typename_parent_id_idx', 'user_id', 'typename', 'parent_id'),
@@ -70,7 +72,7 @@ class Node(ValidatorMixin, Base):
     parent_id     = Column(Integer, ForeignKey('nodes.id', ondelete='CASCADE'))
     parent        = relationship('Node', remote_side=[id])
 
-    name = Column(String(255), nullable=False, server_default='')
+    name = Column(String(NAME_MAXLEN), nullable=False, server_default='')
     date = Column(DateTime(timezone=True), nullable=False,
                   server_default=text('CURRENT_TIMESTAMP'))