Added API spec coverage.

Signed-off-by: dblock <dblock@amazon.com>

.github/workflows/coverage.yml

@@ -0,0 +1,66 @@
+name: API Coverage
+
+on: [push, pull_request]
+
+# git clone git@github.com:dblock/OpenSearch.git
+# cd OpenSearch
+# git remote add upstream git@github.com:opensearch-project/OpenSearch.git
+# git fetch upstream --tags
+# git checkout 2.11.1
+# git checkout -b 2.11.1-api-plugin
+# git cherry-pick ffa9ce9d41ac4d8a15b7041b4c8c60c4d3b1cffc
+# git push origin 2.11.1-api-plugin
+
+env:
+  JAVA_VERSION: 11
+  OPENSEARCH_VERSION: 2.11.1
+
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v2
+      - name: Setup Java
+        uses: actions/setup-java@v1
+        with:
+          java-version: ${{ env.JAVA_VERSION }}
+      - name: Checkout OpenSearch
+        uses: actions/checkout@v2
+        with:
+          repository: 'dblock/OpenSearch'
+          path: OpenSearch
+          ref: ${{ env.OPENSEARCH_VERSION }}-api-plugin
+      - name: Build API Plugin
+        working-directory: ./OpenSearch
+        run: |
+          ./gradlew :server:assemble -Dbuild.snapshot=false
+          ./gradlew :libs:opensearch-core:assemble -Dbuild.snapshot=false
+          ./gradlew :plugins:api:assemble -Dbuild.snapshot=false
+      - name: Install API Plugin
+        run: |
+          echo "FROM opensearchproject/opensearch:${{ env.OPENSEARCH_VERSION }}" >> Dockerfile
+          echo "ADD ./OpenSearch/plugins/api/build/distributions/api-${{ env.OPENSEARCH_VERSION }}.zip /tmp/" >> Dockerfile
+          echo "COPY ./OpenSearch/server/build/distributions/opensearch-${{ env.OPENSEARCH_VERSION }}.jar /usr/share/opensearch/lib/" >> Dockerfile
+          echo "COPY ./OpenSearch/libs/core/build/distributions/opensearch-core-${{ env.OPENSEARCH_VERSION }}.jar /usr/share/opensearch/lib/" >> Dockerfile
+          echo "RUN /usr/share/opensearch/bin/opensearch-plugin install --batch file:/tmp/api-${{ env.OPENSEARCH_VERSION }}.zip" >> Dockerfile
+          cat Dockerfile
+      - name: Build and Run Docker Container
+        run: |
+          docker build . --tag opensearch-with-api-plugin
+          docker run --detach -p 9200:9200 -p 9600:9600 -e "discovery.type=single-node" opensearch-with-api-plugin
+          sleep 30
+      - name: Display OpenSearch Info
+        run: |
+          curl -u admin:admin --insecure https://localhost:9200/ | jq
+      - name: Dump and Compare API
+        run: |
+          curl -u admin:admin --insecure https://localhost:9200/_plugins/api | jq > OpenSearch.auto.openapi.json
+          docker run --mount type=bind,source=.,target=/specs openapitools/openapi-diff:latest /specs/OpenSearch.openapi.json /specs/OpenSearch.auto.openapi.json --out /specs/diff.json
+      - name: Show Diff
+        run: |
+          echo "-------- Missing APIs"
+          cat diff.json | jq '.newEndpoints | group_by(.pathUrl)[] | .[0].pathUrl + ": " + (map(.method) | tostring)' --raw-output
+          echo "-------- Legacy APIs"
+          cat diff.json | jq '.missingEndpoints | group_by(.pathUrl)[] | .[0].pathUrl + ": " + (map(.method) | tostring)' --raw-output
+