fix(gui): convert JATS paragraph markup to HTML

in abstracts.

main/templates/relaton/formatted_string.html

@@ -1,5 +1,11 @@
-{% if val.format == "text/html" %}
-  {{ val.content|default:"N/A"|safe }}
+{% load relaton %}
+
+{% if val.content %}
+  {% if val.format == "text/html" %}
+    {{ val.content|safe }}
+  {% else %}
+    {{ val|to_html|safe }}
+  {% endif %}
 {% else %}
-  {{ val.content|default:"N/A" }}
+  N/A
 {% endif %}

main/templatetags/relaton.py

@@ -1,17 +1,35 @@
-from typing import Any, Set, Tuple, Callable, List, Optional
+from typing import Dict, Any, Set, Tuple, Callable, List, Optional
 from urllib.parse import quote_plus
 import dataclasses
 import json
 
 from django.urls import reverse
 from django import template
 
+from relaton.models.strings import GenericStringValue
+from relaton.serializers.bibxml.abstracts import get_paragraphs
+
 from common.util import as_list
 
 
 register = template.Library()
 
 
+@register.filter
+def to_html(value: Dict[str, str]):
+    """Converts a dictionary representation of Relaton’s
+    :class:`~relaton.models.strings.GenericStringValue`
+    to HTML with paragraph markup.
+    """
+    if isinstance(value, dict) and 'content' in value and 'format' in value:
+        try:
+            gsv = GenericStringValue(**value)
+        except Exception:
+            return value['content']
+        else:
+            return '<p>%s' % '<p>'.join(get_paragraphs(gsv))
+
+
 @register.filter
 def bibitem_link(value: Any):
     """The value can either be a BibliographicItem