Add citext module for case-insensitive string type

The citext module provides a case-insensitive character string type.
Use CIText for QRCodeMixin name column.
name should be case-insensitive to avoid duplicate names.

app/factory.py

@@ -25,6 +25,7 @@ def register_cli(app):
     @app.cli.command()
     def initdb():
         """Create the database tables and initialize them with default values"""
+        db.engine.execute('CREATE EXTENSION IF NOT EXISTS citext')
         db.create_all()
         for instance in defaults:
             db.session.add(instance)

app/models.py

@@ -13,6 +13,7 @@ import uuid
 import qrcode
 from sqlalchemy.types import TypeDecorator, CHAR
 from sqlalchemy.dialects.postgresql import UUID
+from citext import CIText
 from flask_login import UserMixin
 from .extensions import db, login_manager, ldap_manager
 from . import utils
@@ -126,7 +127,7 @@ class User(db.Model, UserMixin):
 
 class QRCodeMixin:
     id = db.Column(db.Integer, primary_key=True)
-    name = db.Column(db.String(50), nullable=False, unique=True)
+    name = db.Column(CIText, nullable=False, unique=True)
 
     def image(self):
         """Return a QRCode image to identify a record

environment.yml

@@ -56,4 +56,5 @@ dependencies:
   - ldap3==2.2.4
   - pyasn1==0.2.3
   - pyjwt==1.4.2
+  - sqlalchemy-citext==1.3.post0
   - visitor==0.1.3