server/tags: replace ILIKE expressions

While it makes sense to use ILIKE in search configs to expose side
effects regarding _ and % for power users to use, it certainly didn't
make sense in places changed by this commit. For example, visiting
/tag/___ led to internal server error.

server/szurubooru/func/tag_categories.py

@@ -1,4 +1,5 @@
 import re
+import sqlalchemy
 from szurubooru import config, db, errors
 from szurubooru.func import util, snapshots, cache
 
@@ -37,7 +38,7 @@ def create_category(name, color):
 def update_category_name(category, name):
     if not name:
         raise InvalidTagCategoryNameError('Name cannot be empty.')
-    expr = db.TagCategory.name.ilike(name)
+    expr = sqlalchemy.func.lower(db.TagCategory.name) == name.lower()
     if category.tag_category_id:
         expr = expr & (db.TagCategory.tag_category_id != category.tag_category_id)
     already_exists = db.session.query(db.TagCategory).filter(expr).count() > 0
@@ -61,7 +62,7 @@ def update_category_color(category, color):
 def try_get_category_by_name(name):
     return db.session \
         .query(db.TagCategory) \
-        .filter(db.TagCategory.name.ilike(name)) \
+        .filter(sqlalchemy.func.lower(db.TagCategory.name) == name.lower()) \
         .one_or_none()
 
 def get_category_by_name(name):

server/szurubooru/func/tags.py

@@ -90,7 +90,7 @@ def try_get_tag_by_name(name):
     return db.session \
         .query(db.Tag) \
         .join(db.TagName) \
-        .filter(db.TagName.name.ilike(name)) \
+        .filter(sqlalchemy.func.lower(db.TagName.name) == name.lower()) \
         .one_or_none()
 
 def get_tag_by_name(name):
@@ -105,7 +105,7 @@ def get_tags_by_names(names):
         return []
     expr = sqlalchemy.sql.false()
     for name in names:
-        expr = expr | db.TagName.name.ilike(name)
+        expr = expr | (sqlalchemy.func.lower(db.TagName.name) == name.lower())
     return db.session.query(db.Tag).join(db.TagName).filter(expr).all()
 
 def get_or_create_tags_by_names(names):
@@ -192,7 +192,7 @@ def update_tag_names(tag, names):
     for name in names:
         if util.value_exceeds_column_size(name, db.TagName.name):
             raise InvalidTagNameError('Name is too long.')
-        expr = expr | db.TagName.name.ilike(name)
+        expr = expr | (sqlalchemy.func.lower(db.TagName.name) == name.lower())
     if tag.tag_id:
         expr = expr & (db.TagName.tag_id != tag.tag_id)
     existing_tags = db.session.query(db.TagName).filter(expr).all()