[Enhancement] aws_bedrockagentcore_gateway_target: Add target_configuration.mcp.api_gateway configuration block

[tabito-hara]

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the library.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

Description

This PR adds target_configuration.mcp.api_gateway configuration block to aws_bedrockagentcore_gateway_target resource.

Relations

Closes #46878

References

https://docs.aws.amazon.com/bedrock-agentcore-control/latest/APIReference/API_CreateGatewayTarget.html

Output from Acceptance Testing

$ make testacc TESTS='TestAccBedrockAgentCoreGatewayTarget_' PKG=bedrockagentcore
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
make: Running acceptance tests on branch: 🌿 f-aws_bedrockagentcore_gateway_target-add_mcp_api_gateway_target 🌿...
TF_ACC=1 go1.25.8 test ./internal/service/bedrockagentcore/... -v -count 1 -parallel 20 -run='TestAccBedrockAgentCoreGatewayTarget_'  -timeout 360m -vet=off
2026/03/14 07:05:57 Creating Terraform AWS Provider (SDKv2-style)...
2026/03/14 07:05:57 Initializing Terraform AWS Provider (SDKv2-style)...
=== RUN   TestAccBedrockAgentCoreGatewayTarget_basic
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_basic
=== RUN   TestAccBedrockAgentCoreGatewayTarget_disappears
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_disappears
=== RUN   TestAccBedrockAgentCoreGatewayTarget_targetConfiguration
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_targetConfiguration
=== RUN   TestAccBedrockAgentCoreGatewayTarget_targetConfigurationMCPServer
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_targetConfigurationMCPServer
=== RUN   TestAccBedrockAgentCoreGatewayTarget_targetConfigurationAPIGateway
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_targetConfigurationAPIGateway
=== RUN   TestAccBedrockAgentCoreGatewayTarget_credentialProvider
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_credentialProvider
=== RUN   TestAccBedrockAgentCoreGatewayTarget_credentialProvider_invalid
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_credentialProvider_invalid
=== RUN   TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration
=== RUN   TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration_invalidHeaders
=== PAUSE TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration_invalidHeaders
=== CONT  TestAccBedrockAgentCoreGatewayTarget_basic
=== CONT  TestAccBedrockAgentCoreGatewayTarget_credentialProvider
=== CONT  TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration
=== CONT  TestAccBedrockAgentCoreGatewayTarget_credentialProvider_invalid
=== CONT  TestAccBedrockAgentCoreGatewayTarget_targetConfigurationMCPServer
=== CONT  TestAccBedrockAgentCoreGatewayTarget_targetConfigurationAPIGateway
=== CONT  TestAccBedrockAgentCoreGatewayTarget_targetConfiguration
=== CONT  TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration_invalidHeaders
=== CONT  TestAccBedrockAgentCoreGatewayTarget_disappears
--- PASS: TestAccBedrockAgentCoreGatewayTarget_basic (73.39s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_disappears (76.08s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_credentialProvider_invalid (82.10s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_targetConfigurationMCPServer (101.67s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration_invalidHeaders (113.39s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_targetConfigurationAPIGateway (136.79s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_metadataConfiguration (140.09s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_credentialProvider (231.69s)
--- PASS: TestAccBedrockAgentCoreGatewayTarget_targetConfiguration (270.13s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/bedrockagentcore   274.718s

[github-actions]

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