Add support for new document page structure

Documents now have their own dedicated DocumentPage
submodel. The old DocumentPage is now called DocumentVersionPage.
This allows mappings between document pages and document version
pages, allowing renumbering, appending pages.
DocumentPages have a content_object to map them to any other
object. For now they only map to DocumentVersionPages.
New option added to the version upload form to append the
pages of the new version.
A new view was added to just append new pages with wraps the
new document version upload form and hides the append pages
checkbox set to True.
Add a new action, reset_pages to reset the pages of the
document to those of the latest version.

Missing: appending tests, checks for proper content_object in OCR and
document parsing.

Author: Roberto Rosario <roberto.rosario@mayan-edms.com>
Date:   Thu Oct 11 12:00:25 2019 -0400

mayan/apps/document_parsing/apps.py

@@ -12,7 +12,9 @@ from mayan.apps.common.classes import ModelField
 from mayan.apps.common.menus import (
     menu_facet, menu_list_facet, menu_multi_item, menu_secondary, menu_tools
 )
-from mayan.apps.documents.search import document_search, document_page_search
+from mayan.apps.documents.search import (
+    document_search, document_page_search, document_version_page_search
+)
 from mayan.apps.documents.signals import post_version_upload
 from mayan.apps.events.classes import ModelEventType
 from mayan.apps.navigation.classes import SourceColumn
@@ -43,7 +45,7 @@ from .permissions import (
     permission_parse_document
 )
 from .signals import post_document_version_parsing
-from .utils import get_document_content
+from .utils import get_document_content, get_document_version_content
 
 logger = logging.getLogger(__name__)
 
@@ -74,6 +76,9 @@ class DocumentParsingApp(MayanAppConfig):
         DocumentVersion = apps.get_model(
             app_label='documents', model_name='DocumentVersion'
         )
+        DocumentVersionPage = apps.get_model(
+            app_label='documents', model_name='DocumentVersionPage'
+        )
         DocumentVersionParseError = self.get_model(
             model_name='DocumentVersionParseError'
         )
@@ -85,7 +90,7 @@ class DocumentParsingApp(MayanAppConfig):
             name='content', value=get_document_content
         )
         DocumentVersion.add_to_class(
-            name='content', value=get_document_content
+            name='content', value=get_document_version_content
         )
         DocumentVersion.add_to_class(
             name='submit_for_parsing',
@@ -100,9 +105,9 @@ class DocumentParsingApp(MayanAppConfig):
             )
         )
 
-        ModelField(
-            model=Document, name='versions__version_pages__content__content'
-        )
+        #ModelField(
+        #    model=Document, name='versions__pages__content__content'
+        #)
 
         ModelPermission.register(
             model=Document, permissions=(
@@ -133,17 +138,17 @@ class DocumentParsingApp(MayanAppConfig):
         )
 
         document_search.add_model_field(
-            field='versions__version_pages__content__content', label=_('Content')
+            field='versions__pages__content__content', label=_('Content')
         )
 
-        document_page_search.add_model_field(
+        document_version_page_search.add_model_field(
             field='content__content', label=_('Content')
         )
 
         menu_facet.bind_links(
             links=(link_document_content,), sources=(Document,)
         )
-        menu_facet.bind_links(
+        menu_list_facet.bind_links(
             links=(link_document_page_content,), sources=(DocumentPage,)
         )
         menu_list_facet.bind_links(