Inherit the platform contract tests, and extend the shared Renovate preset

PlatformWebContract asserts what this app must do because it is on the platform: an /api
path matching no controller 404s rather than returning the SPA, health is UP, the liveness
and readiness probes exist, and a client-side route forwards to the shell. That first one
shipped broken to six live sites and was found by typing a URL by hand; now it fails a
build instead.

renovate.json is three lines pointing at austin/renovate-config. The rules were copied per
repo, so they matched only by luck and a change was six edits.

Platform 0.1.9.

pom.xml

@@ -7,7 +7,7 @@
     <parent>
         <groupId>net.thebennett.platform</groupId>
         <artifactId>platform-parent</artifactId>
-        <version>0.1.7</version>
+        <version>0.1.9</version>
         <relativePath/>
     </parent>
 
@@ -22,7 +22,7 @@
             <dependency>
                 <groupId>net.thebennett.platform</groupId>
                 <artifactId>platform-bom</artifactId>
-                <version>0.1.7</version>
+                <version>0.1.9</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -62,6 +62,12 @@
              is no form to deliver. No starter-security: nothing here to sign in to. -->
 
         <!-- test -->
+        <!-- Contract tests every app on the platform inherits. -->
+        <dependency>
+            <groupId>net.thebennett.platform</groupId>
+            <artifactId>platform-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>