CSV Transaction Imports (#708)

Introduces a basic CSV import module for bulk-importing account transactions.

Changes include:

- User can load a CSV
- User can configure the column mappings for a CSV
- Imported CSV shows invalid cells
- User can clean up their data directly in the UI
- User can see a preview of the import rows and confirm import
- Layout refactor + Import nav stepper
- System test stability improvements

app/controllers/imports_controller.rb

@@ -0,0 +1,102 @@
+require "ostruct"
+
+class ImportsController < ApplicationController
+  before_action :set_import, except: %i[ index new create ]
+
+  def index
+    @imports = Current.family.imports
+    render layout: "with_sidebar"
+  end
+
+  def new
+    @import = Import.new
+  end
+
+  def edit
+  end
+
+  def update
+    account = Current.family.accounts.find(params[:import][:account_id])
+
+    @import.update! account: account
+    redirect_to load_import_path(@import), notice: t(".import_updated")
+  end
+
+  def create
+    account = Current.family.accounts.find(params[:import][:account_id])
+    @import = Import.create!(account: account)
+
+    redirect_to load_import_path(@import), notice: t(".import_created")
+  end
+
+  def destroy
+    @import.destroy!
+    redirect_to imports_url, notice: t(".import_destroyed"), status: :see_other
+  end
+
+  def load
+  end
+
+  def load_csv
+    if @import.update(import_params)
+      redirect_to configure_import_path(@import), notice: t(".import_loaded")
+    else
+      flash.now[:error] = @import.errors.full_messages.to_sentence
+      render :load, status: :unprocessable_entity
+    end
+  end
+
+  def configure
+    unless @import.loaded?
+      redirect_to load_import_path(@import), alert: t(".invalid_csv")
+    end
+  end
+
+  def update_mappings
+    @import.update! import_params(@import.expected_fields.map(&:key))
+    redirect_to clean_import_path(@import), notice: t(".column_mappings_saved")
+  end
+
+  def clean
+    unless @import.loaded?
+      redirect_to load_import_path(@import), alert: t(".invalid_csv")
+    end
+  end
+
+  def update_csv
+    update_params = import_params[:csv_update]
+
+    @import.update_csv! \
+      row_idx: update_params[:row_idx],
+      col_idx: update_params[:col_idx],
+      value: update_params[:value]
+
+    render :clean
+  end
+
+  def confirm
+    unless @import.cleaned?
+      redirect_to clean_import_path(@import), alert: t(".invalid_data")
+    end
+  end
+
+  def publish
+    if @import.valid?
+      @import.publish_later
+      redirect_to imports_path, notice: t(".import_published")
+    else
+      flash.now[:error] = t(".invalid_data")
+      render :confirm, status: :unprocessable_entity
+    end
+  end
+
+  private
+
+    def set_import
+      @import = Current.family.imports.find(params[:id])
+    end
+
+    def import_params(permitted_mappings = nil)
+      params.require(:import).permit(:raw_csv_str, column_mappings: permitted_mappings, csv_update: [ :row_idx, :col_idx, :value ])
+    end
+end