Add OpenAPI specification for Link-Not-Merge Policy APIs

- Introduced a new OpenAPI YAML file for the StellaOps Concelier service.
- Defined endpoints for listing linksets, retrieving linksets by advisory ID, and searching linksets.
- Included detailed parameter specifications and response schemas for each endpoint.
- Established components for reusable parameters and schemas, enhancing API documentation clarity.

src/Concelier/__Tests/StellaOps.Concelier.WebService.Tests/WebServiceEndpointsTests.cs

@@ -311,6 +311,54 @@ public sealed class WebServiceEndpointsTests : IAsyncLifetime
         Assert.True(string.IsNullOrEmpty(secondPayload.NextCursor));
     }
 
+    [Fact]
+    public async Task LnmLinksetsEndpoints_ReturnFactOnlyLinksets()
+    {
+        var tenant = "tenant-lnm-list";
+        var documents = new[]
+        {
+            CreateLinksetDocument(
+                tenant,
+                "nvd",
+                "ADV-002",
+                new[] { "obs-2" },
+                new[] { "pkg:npm/demo@2.0.0" },
+                new[] { "2.0.0" },
+                new DateTime(2025, 1, 6, 0, 0, 0, DateTimeKind.Utc)),
+            CreateLinksetDocument(
+                tenant,
+                "osv",
+                "ADV-001",
+                new[] { "obs-1" },
+                new[] { "pkg:npm/demo@1.0.0" },
+                new[] { "1.0.0" },
+                new DateTime(2025, 1, 5, 0, 0, 0, DateTimeKind.Utc))
+        };
+
+        await SeedLinksetDocumentsAsync(documents);
+
+        using var client = _factory.CreateClient();
+        client.DefaultRequestHeaders.Add("X-Stella-Tenant", tenant);
+
+        var listResponse = await client.GetAsync("/v1/lnm/linksets?pageSize=1&page=1");
+        listResponse.EnsureSuccessStatusCode();
+
+        var listPayload = await listResponse.Content.ReadFromJsonAsync<JsonElement>();
+        var firstItem = listPayload.GetProperty("items").EnumerateArray().First();
+        Assert.Equal("ADV-002", firstItem.GetProperty("advisoryId").GetString());
+        Assert.Contains("pkg:npm/demo@2.0.0", firstItem.GetProperty("purl").EnumerateArray().Select(x => x.GetString()));
+        Assert.True(firstItem.GetProperty("conflicts").EnumerateArray().Count() >= 0);
+
+        var detailResponse = await client.GetAsync("/v1/lnm/linksets/ADV-001?source=osv&includeObservations=true");
+        detailResponse.EnsureSuccessStatusCode();
+
+        var detailPayload = await detailResponse.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.Equal("ADV-001", detailPayload.GetProperty("advisoryId").GetString());
+        Assert.Equal("osv", detailPayload.GetProperty("source").GetString());
+        Assert.Contains("pkg:npm/demo@1.0.0", detailPayload.GetProperty("purl").EnumerateArray().Select(x => x.GetString()));
+        Assert.Contains("obs-1", detailPayload.GetProperty("observations").EnumerateArray().Select(x => x.GetString()));
+    }
+
     [Fact]
     public async Task ObservationsEndpoint_ReturnsBadRequestWhenTenantMissing()
     {