Add OCP 5.1 nightly testconfig and egressip allowlist

Version-pinned osp_verification_5.1_nightly.yaml resolves the
5.1.0-0.nightly stream for pre-GA RHOSO validation on serval71.
Add egressip allowlist entry for 5.1 so egressip_tests can run
without "No allowlist found" failures.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: tusharjadhav3302

collection/stages/roles/egressip_tests/files/egressip-allowlist.yaml

@@ -157,3 +157,8 @@ ovnk_list: &ovnk_tests
 "5.0":
   "OVNKubernetes":
     <<: *ovnk_tests
+
+# OpenShift 5.1
+"5.1":
+  "OVNKubernetes":
+    <<: *ovnk_tests

jobs_definitions/osp_verification_5.1_nightly.yaml

@@ -0,0 +1,58 @@
+---
+#
+#     * OSP VERIFICATION - OCP 5.1 NIGHTLY *
+#
+# - Version-pinned variant of osp_verification.yaml for OCP 5.1 pre-GA nightly.
+# - Enables early regression detection on the next OCP minor stream.
+# - Runs on the RHOSO 18.0 OSASINFRA Validated Architecture (serval71).
+#
+# Note: The sigstore fix env var (nightly_disable_image_policy) is EXPERIMENTAL
+# and may change. Monitor shiftstack-qa/configs/global.yml for updates.
+#
+
+openshift_release: "5.1"
+openshift_build_name: "" # Empty resolves to latest nightly via 5.1.0-0.nightly/latest
+installation_type: ipi
+stages:
+  - prepare
+  - install
+  - post
+  - verification
+  - day2ops
+  - openstack_test
+  - lb_tests
+  - egressip_tests
+
+day2ops_procedures:
+  - rotate_app_creds
+
+ocp_deployment_topology:
+  network_type: OVNKubernetes
+  primary_ip_protocol: ipv4    # ipv4 or ipv6
+  secondary_ip_protocol: ""    # ipv4, ipv6, or "" for single-stack
+  ipv4:
+    ip_version: 4
+    tenant_subnet:
+      cidr: 10.196.0.0/16     # CIDR for the machine network (tenant network)
+    cluster_network:
+      cidr: 10.128.0.0/14
+      host_prefix: 23
+    service_network:
+      - 172.30.0.0/16
+  flavors:
+    master:
+      name: "master"
+      ram: 16384
+      vcpus: 4
+      disk: 30
+    worker:
+      name: "worker"
+      ram: 8192
+      vcpus: 2
+      disk: 30
+  replicas:
+    master: 3
+    worker: 2
+  servergroups:
+    master: "soft-anti-affinity"
+    worker: "soft-anti-affinity"