Make concourse pipeline public

Migrate concourse pipeline to use credhub and expose a limited number
of jobs as "public".

Closes gh-10693

ci/README.adoc

@@ -1,27 +1,15 @@
 == Concourse pipeline
 
-To set the pipeline first create a file in this directory called `secrets.yml`:
-
-[source,yaml]
-.secrets.yml
-----
-docker-hub-username: <user>
-docker-hub-password: <secret>
-github-username: <user>
-github-password: <secret>
-artifactory-username: <user>
-artifactory-password: <secret>
-----
-
-NOTE: The file should be ignored by git, make sure that you don't commit it!
-
-Once the file has been created, the pipeline can be deployed:
+The pipeline can be deployed using the following command:
 
 [source]
 ----
-$ fly -t spring set-pipeline -p spring-boot -c ci/pipeline.yml -l ci/parameters.yml -l ci/secrets.yml
+$ fly -t spring set-pipeline -p spring-boot -c ci/pipeline.yml -l ci/parameters.yml
 ----
 
+NOTE: This assumes that you have credhub integration configured with the appropriate
+secrets
+
 === Release
 
 To release a milestone:

ci/pipeline.yml

@@ -78,6 +78,7 @@ jobs:
       build: ci-images-git-repo/ci/images/spring-boot-jdk9-ci-image
 - name: build
   serial: true
+  public: true
   plan:
   - get: spring-boot-ci-image
   - get: git-repo
@@ -121,6 +122,7 @@ jobs:
           "zip.deployed": "false"
 - name: build-pull-requests
   serial: true
+  public: true
   plan:
   - get: spring-boot-ci-image
   - get: git-repo
@@ -161,6 +163,7 @@ jobs:
         status: failure
 - name: jdk9-build
   serial: true
+  public: true
   plan:
   - get: spring-boot-jdk9-ci-image
   - get: git-repo