Created ECN# autocomplete for PCR3 docs

MesaFabApproval.Client/Services/ECNService.cs

@@ -5,6 +5,7 @@ namespace MesaFabApproval.Client.Services;
 public interface IECNService {
     Task<string> ECNNumberIsValidStr(int ecnNumber);
     Task<bool> ECNNumberIsValid(int number);
+    Task<IEnumerable<int>> GetAllECNNumbers();
 }
 
 public class ECNService : IECNService {
@@ -49,4 +50,32 @@ public class ECNService : IECNService {
             throw new Exception($"Unable to determine if {number} is a valid ECN#, because {ex.Message}");
         }
     }
+
+    public async Task<IEnumerable<int>> GetAllECNNumbers() {
+        try {
+            HttpClient httpClient = _httpClientFactory.CreateClient("API");
+
+            HttpRequestMessage requestMessage = new(HttpMethod.Get, $"ecn/allNumbers");
+
+            HttpResponseMessage responseMessage = await httpClient.SendAsync(requestMessage);
+
+            if (responseMessage.IsSuccessStatusCode) {
+                string responseContent = await responseMessage.Content.ReadAsStringAsync();
+
+                JsonSerializerOptions jsonSerializerOptions = new() {
+                    PropertyNameCaseInsensitive = true
+                };
+
+                IEnumerable<int> allEcnNumbers =
+                    JsonSerializer.Deserialize<IEnumerable<int>>(responseContent, jsonSerializerOptions) ??
+                    new List<int>();
+
+                return allEcnNumbers;
+            } else {
+                throw new Exception(responseMessage.ReasonPhrase);
+            }
+        } catch (Exception ex) {
+            throw new Exception($"Unable to get all ECN#s, because {ex.Message}");
+        }
+    }
 }