bans: change expires_at field to duration.

Changes:

* Change the `expires_at` field to `duration`.
* Make moderators choose from a fixed set of standard ban lengths,
  instead of allowing arbitrary ban lengths.
* List `duration` in seconds in the /bans.json API.
* Dump bans to BigQuery.

Note that some old bans have a negative duration. This is because their
expiration date was before their creation date, which is because in 2013
bans were migrated to Danbooru 2 and the original ban creation dates
were lost.

app/logical/bigquery_export_service.rb

@@ -21,7 +21,7 @@ class BigqueryExportService
     Rails.application.eager_load!
 
     models = ApplicationRecord.descendants.sort_by(&:name)
-    models -= [Ban, Favorite, IpAddress, TagRelationship, ArtistVersion, ArtistCommentaryVersion, NoteVersion, PoolVersion, PostVersion, WikiPageVersion]
+    models -= [Favorite, IpAddress, TagRelationship, ArtistVersion, ArtistCommentaryVersion, NoteVersion, PoolVersion, PostVersion, WikiPageVersion]
     models
   end
 

app/logical/concerns/searchable.rb

@@ -212,7 +212,7 @@ module Searchable
       search_text_attribute(name, params)
     when :boolean
       search_boolean_attribute(name, params)
-    when :integer, :float, :datetime
+    when :integer, :float, :datetime, :interval
       search_numeric_attribute(name, params, type: type)
     when :inet
       search_inet_attribute(name, params)
@@ -221,7 +221,7 @@ module Searchable
     when :array
       search_array_attribute(name, subtype, params)
     else
-      raise NotImplementedError, "unhandled attribute type: #{name}"
+      raise NotImplementedError, "unhandled attribute type: #{name} (#{type})"
     end
   end
 

app/logical/post_query_builder.rb

@@ -740,6 +740,9 @@ class PostQueryBuilder
       when :age
         DurationParser.parse(object).ago
 
+      when :interval
+        DurationParser.parse(object)
+
       when :ratio
         object =~ /\A(\d+(?:\.\d+)?):(\d+(?:\.\d+)?)\Z/i
 
@@ -765,6 +768,9 @@ class PostQueryBuilder
         end
 
         (size * conversion_factor).to_i
+
+      else
+        raise NotImplementedError, "unrecognized type #{type} for #{object}"
       end
     end