feat(rollup): add models and write path [1/3] (#13796)

## PR#1: Reporting events rollup — model and write path

Reporting queries currently hit the `reporting_events` table directly.
This works, but the table grows linearly with event volume, and
aggregation queries (counts, averages over date ranges) get
progressively slower as accounts age.

This PR introduces a pre-aggregated `reporting_events_rollups` table
that stores daily per-metric, per-dimension (account/agent/inbox)
totals. The write path is intentionally decoupled from the read path —
rollup rows are written inline from the event listener via upsert, and a
backfill service exists to rebuild historical data from raw events.
Nothing reads from this table yet.

The write path activates when an account has a `reporting_timezone` set
(new account setting). The `reporting_events_rollup` feature flag
controls only the future read path, not writes — so rollup data
accumulates silently once timezone is configured. A `MetricRegistry`
maps raw event names to rollup column semantics in one place, keeping
the write and (future) read paths aligned.

### What changed

- Migration for `reporting_events_rollups` with a unique composite index
for upsert
- `ReportingEventsRollup` model
- `reporting_timezone` account setting with IANA timezone validation
- `MetricRegistry` — single source of truth for event-to-metric mappings
- `RollupService` — real-time upsert from event listener
- `BackfillService` — rebuilds rollups for a given account + date from
raw events
- Rake tasks for interactive backfill and timezone setup
- `reporting_events_rollup` feature flag (disabled by default)

### How to test

1. Set a `reporting_timezone` on an account
(`Account.first.update!(reporting_timezone: 'Asia/Kolkata')`)
2. Resolve a conversation or trigger a first response
3. Check `ReportingEventsRollup.where(account_id: ...)` — rows should
appear
4. Run backfill: `bundle exec rake reporting_events_rollup:backfill` and
verify historical data populates

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/models/account.rb

@@ -85,11 +85,13 @@ class Account < ApplicationRecord
   validates_with JsonSchemaValidator,
                  schema: SETTINGS_PARAMS_SCHEMA,
                  attribute_resolver: ->(record) { record.settings }
+  validate :validate_reporting_timezone
 
   store_accessor :settings, :auto_resolve_after, :auto_resolve_message, :auto_resolve_ignore_waiting
 
   store_accessor :settings, :audio_transcriptions, :auto_resolve_label
   store_accessor :settings, :captain_models, :captain_features
+  store_accessor :settings, :reporting_timezone
   store_accessor :settings, :keep_pending_on_bot_failure
   store_accessor :settings, :captain_auto_resolve_mode
   include AccountCaptainAutoResolve
@@ -215,6 +217,12 @@ class Account < ApplicationRecord
     # method overridden in enterprise module
   end
 
+  def validate_reporting_timezone
+    return if reporting_timezone.blank? || ActiveSupport::TimeZone[reporting_timezone].present?
+
+    errors.add(:reporting_timezone, I18n.t('errors.account.reporting_timezone.invalid'))
+  end
+
   def remove_account_sequences
     ActiveRecord::Base.connection.exec_query("drop sequence IF EXISTS camp_dpid_seq_#{id}")
     ActiveRecord::Base.connection.exec_query("drop sequence IF EXISTS conv_dpid_seq_#{id}")

app/models/reporting_events_rollup.rb

@@ -0,0 +1,48 @@
+# == Schema Information
+#
+# Table name: reporting_events_rollups
+#
+#  id                        :bigint           not null, primary key
+#  count                     :bigint           default(0), not null
+#  date                      :date             not null
+#  dimension_id              :bigint           not null
+#  dimension_type            :string           not null
+#  metric                    :string           not null
+#  sum_value                 :float            default(0.0), not null
+#  sum_value_business_hours  :float            default(0.0), not null
+#  created_at                :datetime         not null
+#  updated_at                :datetime         not null
+#  account_id                :integer          not null
+#
+# Indexes
+#
+#  index_rollup_summary     (account_id,dimension_type,date)
+#  index_rollup_timeseries  (account_id,metric,date)
+#  index_rollup_unique_key  (account_id,date,dimension_type,dimension_id,metric) UNIQUE
+#
+
+class ReportingEventsRollup < ApplicationRecord
+  belongs_to :account
+
+  # Store string values directly in the database for better readability and debugging
+  enum :dimension_type, %w[account agent inbox team].index_by(&:itself)
+  enum :metric, %w[
+    resolutions_count
+    first_response
+    resolution_time
+    reply_time
+    bot_resolutions_count
+    bot_handoffs_count
+  ].index_by(&:itself)
+
+  validates :account_id, presence: true
+  validates :date, presence: true
+  validates :dimension_type, presence: true
+  validates :dimension_id, presence: true
+  validates :metric, presence: true
+  validates :count, numericality: { greater_than_or_equal_to: 0 }
+
+  scope :for_date_range, ->(start_date, end_date) { where(date: start_date..end_date) }
+  scope :for_dimension, ->(type, id) { where(dimension_type: type, dimension_id: id) }
+  scope :for_metric, ->(metric) { where(metric: metric) }
+end