Name filters use istartswith on most endpoints — substring search misses; inconsistent with activations/rulebooks

[amasolov]

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Bug Summary

Six of the nine list endpoints used by the EDA role wizard filter name with lookup_expr="istartswith", while three use icontains, so substring search silently misses on most endpoints — and the ansible-ui toolbar presents the filter as a "contains" search:

Endpoint	name lookup
eda-credentials, projects, credential-types, decision-environments, event-streams	istartswith
activations, rulebooks, activation-instances	icontains
audit-rules	no filterset_class at all

(See src/aap_eda/api/filters/*.py.)

Clients also cannot work around this with ?name__icontains=: no FilterSet declares that lookup, and with no django-filter STRICTNESS configured the unknown param is silently ignored, returning the full unfiltered list.

Environment

AAP 2.7 on OpenShift (eda-server-operator), EDA API version 1.3.2. Behavior is defined in the FilterSet declarations, so it is deployment-independent (same in standalone builds).

Steps to reproduce

1. On an instance with the default credential types loaded, call GET /api/eda/v1/credential-types/?name=auth.
2. Call GET /api/eda/v1/credential-types/?name__icontains=basic.

Actual results

1. ?name=auth returns 0 results, even though "OAuth2 Event Stream" and "OAuth2 JWT Event Stream" exist (prefix-only match).
2. ?name__icontains=basic returns all 28 credential types (param silently ignored, no filtering).

Expected results

1. A name search presented as "contains" in the UI should match substrings: ?name=auth should return the two OAuth2 types.
2. Ideally an unsupported filter param should not silently return the full unfiltered collection.

Additional information

Suggested fix: change lookup_expr to icontains for the istartswith name filters (precedent already in-tree: ActivationFilter, RulebookFilter), and consider adding a filterset_class to AuditRuleViewSet. Backward-compatible: icontains matches are a strict superset of istartswith matches.

Refs: ansible/ansible-ui#3322 (where this was uncovered), ansible/django-ansible-base#1060 (related OPTIONS metadata regression found in the same investigation).