feat: Add an API to support querying metrics by ChannelType (#13255)

This API gives you how many conversations exist per channel, broken down
by status in a given time period. The max time period is capped to 6
months for now.

**Input Params:**
- **since:** Unix timestamp (seconds) - start of date range
- **until:** Unix timestamp (seconds) - end of date range


**Response Payload:**

```json
{
  "Channel::Sms": {
    "resolved": 85,
    "snoozed": 10,
    "open": 5,
    "pending": 5,
    "total": 100
  },
  "Channel::Email": {
    "resolved": 72,
    "snoozed": 15,
    "open": 13,
    "pending": 13,
    "total": 100
  },
  "Channel::WebWidget": {
    "resolved": 90,
    "snoozed": 7,
    "open": 3,
    "pending": 3,
    "total": 100
  }
}
```

**Definitons:**
resolved = Number of conversations created within the selected time
period that are currently marked as resolved.
snoozed = Number of conversations created within the selected time
period that are currently marked as snoozed.
pending = Number of conversations created within the selected time
period that are currently marked as pending.
open = Number of conversations created within the selected time period
that are currently open.
total = Total number of conversations created within the selected time
period, across all statuses.

app/controllers/api/v2/accounts/summary_reports_controller.rb

@@ -1,6 +1,6 @@
 class Api::V2::Accounts::SummaryReportsController < Api::V1::Accounts::BaseController
   before_action :check_authorization
-  before_action :prepare_builder_params, only: [:agent, :team, :inbox, :label]
+  before_action :prepare_builder_params, only: [:agent, :team, :inbox, :label, :channel]
 
   def agent
     render_report_with(V2::Reports::AgentSummaryBuilder)
@@ -18,6 +18,12 @@ class Api::V2::Accounts::SummaryReportsController < Api::V1::Accounts::BaseContr
     render_report_with(V2::Reports::LabelSummaryBuilder)
   end
 
+  def channel
+    return render_could_not_create_error(I18n.t('errors.reports.date_range_too_long')) if date_range_too_long?
+
+    render_report_with(V2::Reports::ChannelSummaryBuilder)
+  end
+
   private
 
   def check_authorization
@@ -40,4 +46,12 @@ class Api::V2::Accounts::SummaryReportsController < Api::V1::Accounts::BaseContr
   def permitted_params
     params.permit(:since, :until, :business_hours)
   end
+
+  def date_range_too_long?
+    return false if permitted_params[:since].blank? || permitted_params[:until].blank?
+
+    since_time = Time.zone.at(permitted_params[:since].to_i)
+    until_time = Time.zone.at(permitted_params[:until].to_i)
+    (until_time - since_time) > 6.months
+  end
 end