Publish to artifactory (#374)

## Summary

- artifacts publications have been disabled since [2.5.11](https://github.com/linkedin/kafka-monitor/releases/tag/)
- which prevents apps that depend on KM to update to the latest versions
- PR adds Github Action to publish to JFrog Artifactory on release tag creation
- as well as Artifactory and Gradle integration

## Testing Done
1. [workflow ran successfully](https://github.com/linkedin/kafka-monitor/runs/8278325597?check_suite_focus=true#step:6:39) and 
2. publish went through — [test version 0.0.0 in JFROG](https://linkedin.jfrog.io/ui/packages/gav:%2F%2Fcom.linkedin.kmf:kafka-monitor/0.0.0?name=kafka-monitor&type=packages&activeTab=builds)

.github/workflows/tag.yml

@@ -0,0 +1,34 @@
+name: tag (release) flow
+
+on:
+  create:
+    tags:
+      - '*'
+
+jobs:
+  gradle-java8:
+    name: Java 8 release
+    runs-on: ubuntu-latest
+    steps:
+    - name: checkout code
+      uses: actions/checkout@v2
+      with:
+        # bring in all history because the gradle versions plugin needs to "walk back" to the closest ancestor tag
+        # to figure out what version this is. optimizing this is left as a challenge to future committers
+        fetch-depth: 0
+    - name: Set up JDK 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - name: Build with Gradle
+        # add --info or --debug below for more details when trying to understand issues
+      run: ./gradlew clean build javadoc --stacktrace --warning-mode all --no-daemon
+    - name: Branch tag
+      id: branch_tag
+      run: echo ::set-output name=RELEASE_TAG::${GITHUB_REF#refs/tags/}
+    - name: Publish to Jfrog
+      env:
+        JFROG_USER: ${{ secrets.JFROG_USER }}
+        JFROG_KEY: ${{ secrets.JFROG_KEY }}
+        RELEASE_TAG: ${{ steps.branch_tag.outputs.RELEASE_TAG }}
+      run: ./scripts/publishToJfrog.sh

build.gradle

@@ -121,6 +121,20 @@ allprojects {
             url = 'https://github.com/linkedin/kafka-monitor'
           }
         }
+
+        repositories {
+          mavenLocal()
+          maven {
+            name "LinkedInJfrog"
+            url "https://linkedin.jfrog.io/artifactory/kafka-monitor"
+            credentials {
+              if (System.getenv('JFROG_USER') != null && System.getenv('JFROG_KEY') != null) {
+                username System.getenv('JFROG_USER')
+                password System.getenv('JFROG_KEY')
+              }
+            }
+          }
+        }
       }
     }
   }

scripts/publishToJfrog.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+result=${PWD##*/}
+if [[ "$result" = "scripts" ]]
+then
+    echo "script must be run from root project folder, not $PWD"
+    exit 1
+else
+    echo "we are in $PWD and tag is $RELEASE_TAG"
+
+    if [[ $RELEASE_TAG =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]
+    then
+        echo "publishing: tag $RELEASE_TAG looks like a semver"
+        git status
+        git describe --tags
+        ./gradlew printVersion
+        ./gradlew publishMyPublicationPublicationToLinkedInJfrogRepository
+    else
+        echo "not publishing: tag $RELEASE_TAG is NOT a valid semantic version (x.y.z)"
+    fi
+fi