Add migration to add ALIAS columns to common session/visit properties (#4058)

This allows for simplifications in the API code

priv/ingest_repo/migrations/20240502115822_alias_api_prop_names.exs

@@ -0,0 +1,81 @@
+defmodule Plausible.IngestRepo.Migrations.AliasApiPropNames do
+  """
+  Migration adds a ALIAS columns needed to keep DB schema and api
+  property naming in sync to reduce overhead in code.
+  """
+
+  use Ecto.Migration
+
+  @sessions_prop_names %{
+    "source" => "referrer_source",
+    "device" => "screen_size",
+    "screen" => "screen_size",
+    "os" => "operating_system",
+    "os_version" => "operating_system_version",
+    "country" => "country_code",
+    "region" => "subdivision1_code",
+    "city" => "city_geoname_id",
+    "entry_page_hostname" => "hostname"
+  }
+
+  @events_prop_names %{
+    "source" => "referrer_source",
+    "device" => "screen_size",
+    "screen" => "screen_size",
+    "os" => "operating_system",
+    "os_version" => "operating_system_version",
+    "country" => "country_code",
+    "region" => "subdivision1_code",
+    "city" => "city_geoname_id"
+  }
+
+  def up do
+    column_types = get_column_types()
+    on_cluster = Plausible.MigrationUtils.on_cluster_statement("sessions_v2")
+
+    for {alias_name, column_name} <- @sessions_prop_names do
+      execute """
+      ALTER TABLE sessions_v2
+      #{on_cluster}
+      ADD COLUMN #{alias_name} #{Map.fetch!(column_types, column_name)} ALIAS #{column_name}
+      """
+    end
+
+    for {alias_name, column_name} <- @events_prop_names do
+      execute """
+      ALTER TABLE events_v2
+      #{on_cluster}
+      ADD COLUMN #{alias_name} #{Map.fetch!(column_types, column_name)} ALIAS #{column_name}
+      """
+    end
+  end
+
+  def down do
+    on_cluster = Plausible.MigrationUtils.on_cluster_statement("sessions_v2")
+
+    for {alias_name, column_name} <- @sessions_prop_names do
+      execute """
+      ALTER TABLE sessions_v2
+      #{on_cluster}
+      DROP COLUMN #{alias_name}
+      """
+    end
+
+    for {alias_name, column_name} <- @events_prop_names do
+      execute """
+      ALTER TABLE events_v2
+      #{on_cluster}
+      DROP COLUMN #{alias_name}
+      """
+    end
+  end
+
+  def get_column_types() do
+    %{rows: rows} =
+      Plausible.IngestRepo.query!("""
+        SELECT name, type FROM system.columns WHERE table = 'sessions_v2'
+      """)
+
+    Map.new(rows, fn [name, type] -> {name, type} end)
+  end
+end