Merge ADT dataplane feature branch into master. (Azure#14089)

pom.xml

@@ -18,6 +18,7 @@
     <module>sdk/core</module>
     <module>sdk/cosmos</module>
     <module>sdk/cognitiveservices</module>
+    <module>sdk/digitaltwins</module>
     <module>sdk/eventgrid</module>
     <module>sdk/eventhubs</module>
     <module>sdk/formrecognizer</module>

sdk/digitaltwins/azure-digitaltwins-core/Readme.md

@@ -0,0 +1,94 @@
+# Azure IoT Digital Twins client library for Java
+
+This library provides access to the Azure Digital Twins service for managing twins, models, relationships, etc.
+
+  [Source code][source] | Package (maven) (TODO: Add package info)
+
+## Getting started
+
+The complete Microsoft Azure SDK can be downloaded from the [Microsoft Azure downloads][microsoft_sdk_download] page, and it ships with support for building deployment packages, integrating with tooling, rich command line tooling, and more.
+
+For the best development experience, developers should use the official Microsoft Maven packages for libraries. Maven packages are regularly updated with new functionality and hotfixes.
+
+### Install the package
+
+Install the Azure Digital Twins client library for java
+TODO: Fill in details after first publish
+
+### Prerequisites
+
+- A Microsoft Azure Subscription
+  - To call Microsoft Azure services, create an [Azure subscription][azure_sub].
+- An Azure Digital Twins instance
+  - In order to use the Azure Digital Twins SDK, first create a Digital Twins instance using one of options:
+    - Using [Azure portal][azure_portal]
+    - Using [Azure Management APIs][azure_rest_api]
+    - Using [Azure CLI][azure_cli]
+      - You will need to install azure cli and the [Azure IoT extension][iot_cli_extension] for Azure CLI.
+      - Refer to [IoT CLI documentation][iot_cli_doc] for more information on how to create and interact with your Digital Twins instance.
+
+### Authenticate the Client
+
+In order to interact with the Azure Digital Twins service, you will need to create an instance of a [TokenCredential class][token_credential] and pass it to the constructor of your DigitalTwinsClientBuilder (TODO: Reference the file once checked in).
+
+## Key concepts
+
+Azure Digital Twins Preview is an Azure IoT service that creates comprehensive models of the physical environment.
+It can create spatial intelligence graphs to model the relationships and interactions between people, spaces, and devices.
+
+You can learn more about Azure Digital Twins by visiting [Azure Digital Twins Documentation][digital_twins_documentation]
+
+## Examples
+
+You can familiarize yourself with different APIs using [samples for Digital Twins](TODO: Point to sampels once available).
+
+## Source code folder structure
+
+### /src
+
+TODO: Describe source and link to the path.
+
+### /src/swagger
+
+A local copy of the swagger file that defines the structure of the REST APIs supported by the Azure Digital Twins service.
+
+To regenerate the code, run the powershell script [generate.ps1](./generate.ps1).
+
+Any time the client library code is updated, the following scripts need to be run:
+
+TODO: Add extra information here.
+
+## Troubleshooting
+
+TODO: Add troubleshoooting guide
+
+## Next steps
+
+## Contributing
+
+This project welcomes contributions and suggestions.
+Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution.
+For details, visit <https://cla.microsoft.com.>
+
+When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment).
+Simply follow the instructions provided by the bot.
+You will only need to do this once across all repos using our CLA.
+
+This project has adopted the [Microsoft Open Source Code of Conduct][code_of_conduct].
+For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
+
+<!-- LINKS -->
+[microsoft_sdk_download]: https://azure.microsoft.com/en-us/downloads/?sdk=java
+[azure_cli]: https://docs.microsoft.com/cli/azure
+[azure_sub]: https://azure.microsoft.com/free/
+[source]: https://github.com/Azure/azure-sdk-for-java/tree/feature/adt-dp/sdk/digitaltwins/azure-digitaltwins-core
+[code_of_conduct]: https://opensource.microsoft.com/codeofconduct/
+[nuget]: https://www.nuget.org/
+[azure_portal]: https://portal.azure.com/
+[azure_rest_api]: https://docs.microsoft.com/en-us/rest/api/azure/
+[azure_core_library]: https://github.com/Azure/azure-sdk-for-java/tree/master/sdk/core/azure-core
+[token_credential]: https://docs.microsoft.com/en-us/java/api/com.azure.core.credential.tokencredential?view=azure-java-stable
+[digital_twins_documentation]: https://docs.microsoft.com/en-us/azure/digital-twins/
+[azure_cli]: https://docs.microsoft.com/en-us/cli/azure/install-azure-cli?view=azure-cli-latest
+[iot_cli_extension]: https://docs.microsoft.com/en-us/azure/iot-pnp/howto-use-iot-pnp-cli
+[iot_cli_doc]: https://docs.microsoft.com/en-us/cli/azure/ext/azure-iot/dt?view=azure-cli-latest

sdk/digitaltwins/azure-digitaltwins-core/autorest.md

@@ -0,0 +1,21 @@
+# Azure.DigitalTwins.Core
+
+Run `generate.ps1` in this directory to generate the code.
+
+## AutoRest Configuration
+
+> see <https://aka.ms/autorest>
+
+### Code generation settings
+
+``` yaml
+input-file: swagger/digitaltwins.json
+output-folder: "./"
+license-header: MICROSOFT_MIT_SMALL
+use: '@autorest/java@4.0.1'
+java:
+    add-context-parameter: true
+    namespace: com.azure.digitaltwins.core
+    add-credentials: true
+    sync-methods: none
+```