feat: add requirement reference-coverage pie charts and 'Referenced by' column

Add per-requirement reference-coverage pie charts to the platform
verification report, showing how many requirements are referenced by at
least one lower-hierarchy requirement (stakeholder <- feature requirement,
feature requirement <- component requirement). Only references within the
report version scope are counted. Component requirements have no lower
level, so no chart is generated.

The stakeholder and feature requirement tables gain a 'Referenced by'
column (derived_from_back) listing referencing requirements.

Author: antonkri

src/needs_templates/platform_verification_report.need

@@ -104,6 +104,23 @@
 Stakeholder Requirements
 ------------------------
 
+{#- Reference coverage: a stakeholder requirement is "referenced" when at least
+    one in-scope feature requirement is ``derived_from`` it. Only references
+    from requirements inside ``report_version`` scope are counted. -#}
+{% set ns_stkh_ref = namespace(referenced=[], missing=[]) %}
+{% for req_id in ns_stkh_reqs.list %}
+{% set ns_low = namespace(found=false) %}
+{% for low in linked_needs(req_id, "derived_from_back") %}
+{% if low["type"] == "feat_req" and req_in_report_version(low, report_version) %}
+{% set ns_low.found = true %}
+{% endif %}
+{% endfor %}
+{% if ns_low.found %}
+{% set ns_stkh_ref.referenced = ns_stkh_ref.referenced + [req_id] %}
+{% else %}
+{% set ns_stkh_ref.missing = ns_stkh_ref.missing + [req_id] %}
+{% endif %}
+{% endfor %}
 .. grid:: 1 2 2 2
    :gutter: 3
 
@@ -128,14 +145,24 @@ Stakeholder Requirements
          type == "stkh_req" and partially_verifies_back and not fully_verifies_back and {{ stkh_req_filter }}
          type == "stkh_req" and not fully_verifies_back and not partially_verifies_back and {{ stkh_req_filter }}
 
+   .. grid-item::
+
+      .. needpie:: Stakeholder Requirements Reference Coverage
+         :labels: referenced by lower, not referenced
+         :colors: #37a12d, #ca2828
+         :legend:
+
+         id in {{ id_filter_list(ns_stkh_ref.referenced) }}
+         id in {{ id_filter_list(ns_stkh_ref.missing) }}
+
 .. dropdown:: Show requirements table
    :animate: fade-in
 
    .. needtable::
       :filter: type == "stkh_req" and {{ stkh_req_filter }}
       :style: table
-      :columns: id;title;safety;status;testlink
-      :colwidths: 13,22,8,10,47
+      :columns: id;title;safety;status;testlink;derived_from_back as "Referenced by"
+      :colwidths: 12,20,7,9,32,20
       :sort: id
 
 {# ===================================================================== #}
@@ -181,6 +208,22 @@ Feature Overview
 {% endif %}
 {% endfor %}
 {% set feature_req_filter = 'id in ' ~ id_filter_list(ns.req_ids) %}
+{#- Reference coverage: a feature requirement is "referenced" when at least one
+    in-scope component requirement is ``derived_from`` it. -#}
+{% set ns_feat_ref = namespace(referenced=[], missing=[]) %}
+{% for req_id in ns.req_ids %}
+{% set ns_low = namespace(found=false) %}
+{% for low in linked_needs(req_id, "derived_from_back") %}
+{% if low["type"] == "comp_req" and req_in_report_version(low, report_version) %}
+{% set ns_low.found = true %}
+{% endif %}
+{% endfor %}
+{% if ns_low.found %}
+{% set ns_feat_ref.referenced = ns_feat_ref.referenced + [req_id] %}
+{% else %}
+{% set ns_feat_ref.missing = ns_feat_ref.missing + [req_id] %}
+{% endif %}
+{% endfor %}
 Requirements Statistics
 ^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -208,14 +251,24 @@ Requirements Statistics
          type == "feat_req" and "{{ feature_id }}" in satisfied_by and partially_verifies_back and not fully_verifies_back and {{ feature_req_filter }}
          type == "feat_req" and "{{ feature_id }}" in satisfied_by and not fully_verifies_back and not partially_verifies_back and {{ feature_req_filter }}
 
+   .. grid-item::
+
+      .. needpie:: {{ feature_title }} Requirements Reference Coverage
+         :labels: referenced by lower, not referenced
+         :colors: #37a12d, #ca2828
+         :legend:
+
+         id in {{ id_filter_list(ns_feat_ref.referenced) }}
+         id in {{ id_filter_list(ns_feat_ref.missing) }}
+
 .. dropdown:: Show requirements table
    :animate: fade-in
 
    .. needtable::
       :filter: type == "feat_req" and "{{ feature_id }}" in satisfied_by and {{ feature_req_filter }}
       :style: table
-      :columns: id;title;safety;status;testlink
-      :colwidths: 13,22,8,10,47
+      :columns: id;title;safety;status;testlink;derived_from_back as "Referenced by"
+      :colwidths: 12,20,7,9,32,20
       :sort: id
 
 Architecture Statistics