Move Onebranch docker file out of .pipelines directory (#2142)

## Why make this change?

- folders with name `.*` is not being checked out in one branch. So,
`.pipelines` folder is not being checked out.

## What is this change?
- So to access the new one branch docker file i'm moving it out of
.pipelines folder.

## How was this tested?

- accesseble in pipeline

---------

Co-authored-by: Sean Leonard <sean.leonard@microsoft.com>

Author: abhishekkumams

Dockerfile

@@ -4,15 +4,20 @@
 # Version values referenced from https://hub.docker.com/_/microsoft-dotnet-aspnet
 
 FROM mcr.microsoft.com/dotnet/sdk:6.0-cbl-mariner2.0. AS build
-
-
 WORKDIR /src
-COPY [".", "./"]
-RUN dotnet build "./src/Service/Azure.DataApiBuilder.Service.csproj" -c Docker -o /out -r linux-x64
-
 FROM mcr.microsoft.com/dotnet/aspnet:6.0-cbl-mariner2.0 AS runtime
 
-COPY --from=build /out /App
+# The ./src/out path below points to the finalized build bits created by the pipeline.
+# The path is relative to the "Docker build context" specified by the parameter dockerFileContextPath
+# in task: onebranch.pipeline.imagebuildinfo@1
+# The "Docker build context" contains all the files that will be used by the command "docker build"
+# OneBranch uses the injected task Copy Artifacts to
+# copy artifacts from pipeline artifacts: "/mnt/{...}/out" 
+# to the container running the docker tasks: /mnt/{...}/docker/artifacts/
+COPY ./src/out/engine/net6.0 /App
+
+# Change working directory to the /App folder within the Docker image and configure
+# how Data Api buider is started when the container runs.
 WORKDIR /App
 ENV ASPNETCORE_URLS=http://+:5000
 ENTRYPOINT ["dotnet", "Azure.DataApiBuilder.Service.dll"]