Fix broken default value in schema for item description

Idk how we got into this state, or if it's environment-dependent or
MySQL-version-dependent or what, but setting up the dev environment on
my macOS machine is complaining that `TEXT` columns can't have default
values.

Well, in that case, let's just have it be a non-nullable field, and add
a note to our code that missing fields *can* cause item saving to fail!
(This was always true, but I'm just extra-noting it because it's
becoming *more* true.)

app/models/item.rb

@@ -429,6 +429,8 @@ class Item < ApplicationRecord
     species_support_strs = info['species_support'] || []
     self.species_support_ids = species_support_strs.map(&:to_i)
 
+    # NOTE: If some of these fields are missing, it could cause saving the item
+    # to fail, because many of these columns are non-nullable.
     self.name = info['name']
     self.description = info['description']
     self.thumbnail_url = info['thumbnail_url']

db/migrate/20240502195157_fix_default_value_for_items_description.rb

@@ -0,0 +1,8 @@
+class FixDefaultValueForItemsDescription < ActiveRecord::Migration[7.1]
+  def change
+    # Idk why, but this column's default value is specified in our schema as
+    # an empty string, but setting up the dev environment on my macOS machine
+    # is saying on latest MariaDB that this isn't allowed.
+    change_column_default :items, :description, from: "", to: nil
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2024_04_21_033509) do
+ActiveRecord::Schema[7.1].define(version: 2024_05_02_195157) do
   create_table "alt_styles", charset: "utf8mb4", collation: "utf8mb4_unicode_520_ci", force: :cascade do |t|
     t.integer "species_id", null: false
     t.integer "color_id", null: false
@@ -132,7 +132,7 @@ ActiveRecord::Schema[7.1].define(version: 2024_04_21_033509) do
     t.column "modeling_status_hint", "enum('done','glitchy')"
     t.boolean "is_manually_nc", default: false, null: false
     t.string "name", null: false
-    t.text "description", size: :medium, default: "", null: false
+    t.text "description", size: :medium, null: false
     t.string "rarity", default: "", null: false
     t.index ["modeling_status_hint", "created_at", "id"], name: "items_modeling_status_hint_and_created_at_and_id"
     t.index ["modeling_status_hint", "created_at"], name: "items_modeling_status_hint_and_created_at"
@@ -149,7 +149,7 @@ ActiveRecord::Schema[7.1].define(version: 2024_04_21_033509) do
   end
 
   create_table "modeling_logs", id: :integer, charset: "utf8mb4", collation: "utf8mb4_unicode_520_ci", force: :cascade do |t|
-    t.datetime "created_at", precision: nil, default: -> { "current_timestamp()" }, null: false
+    t.datetime "created_at", precision: nil, default: -> { "CURRENT_TIMESTAMP" }, null: false
     t.text "log_json", size: :long, null: false
     t.string "pet_name", limit: 128, null: false
   end