fix: Use WireMock Admin API for dynamic mapping addition

- Replace file copy approach with Admin API POST request
- Use temporary file to avoid complex JSON escaping issues
- Update tests to verify mapping addition success via ExecResult
- Ensures mappings are immediately active without reload delays

This fixes the test failure where mappings added via file copy were not
immediately available to WireMock.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: thomhurst

src/Testcontainers.WireMock/WireMockContainer.cs

@@ -37,12 +37,22 @@ public string GetAdminUrl()
     /// <param name="mappingJson">The mapping JSON content.</param>
     /// <param name="ct">Cancellation token.</param>
     /// <returns>Task that completes when the mapping has been added.</returns>
-    public async Task AddMappingFromJsonAsync(string mappingJson, CancellationToken ct = default)
+    public async Task<ExecResult> AddMappingFromJsonAsync(string mappingJson, CancellationToken ct = default)
     {
-        var mappingFilePath = $"/home/wiremock/mappings/{Guid.NewGuid():N}.json";
+        // Write mapping to a temporary file first, then use curl to post it
+        var tempFile = $"/tmp/mapping_{Guid.NewGuid():N}.json";
+        await CopyAsync(Encoding.UTF8.GetBytes(mappingJson), tempFile, Unix.FileMode644, ct)
+            .ConfigureAwait(false);
+        
+        var result = await ExecAsync(new[] { "curl", "-X", "POST", "http://localhost:8080/__admin/mappings", 
+            "-H", "Content-Type: application/json", "-d", $"@{tempFile}" }, ct)
+            .ConfigureAwait(false);
 
-        await CopyAsync(Encoding.UTF8.GetBytes(mappingJson), mappingFilePath, Unix.FileMode644, ct)
+        // Clean up temp file
+        await ExecAsync(new[] { "rm", tempFile }, ct)
             .ConfigureAwait(false);
+        
+        return result;
     }
 
     /// <summary>

tests/Testcontainers.WireMock.Tests/WireMockContainerTest.cs

@@ -53,12 +53,11 @@ public async Task CanAddMappingAndReceiveStubResponse()
         }";
 
         // When
-        await _wireMockContainer.AddMappingFromJsonAsync(mappingJson)
-            .ConfigureAwait(false);
-
-        // Give WireMock time to process the mapping
-        await Task.Delay(1000)
+        var result = await _wireMockContainer.AddMappingFromJsonAsync(mappingJson)
             .ConfigureAwait(false);
+        
+        // Verify mapping was added successfully
+        Assert.Equal(0, result.ExitCode);
 
         using var httpClient = new HttpClient();
         httpClient.BaseAddress = new Uri(_wireMockContainer.GetBaseUrl());
@@ -89,8 +88,9 @@ public async Task CanResetMappings()
             }
         }";
 
-        await _wireMockContainer.AddMappingFromJsonAsync(mappingJson)
+        var addResult = await _wireMockContainer.AddMappingFromJsonAsync(mappingJson)
             .ConfigureAwait(false);
+        Assert.Equal(0, addResult.ExitCode);
 
         // When
         var execResult = await _wireMockContainer.ResetAsync()