Allow setting external dockerfile for xacml-pdp

If building with an external dockerfile, e.g. using
 mvn clean install -Pdocker -DdockerFile=/path/to/dockerfile
docker will look for project files in the same directory as the
new dockerfile. A new property is added for setting the context
path, to allow using existing project files in src/main/docker.

Issue-ID: POLICY-4334
Signed-off-by: danielhanrahan <daniel.hanrahan@est.tech>
Change-Id: I58953f427fbc3194058a8a07ada508775ff397d4
diff --git a/packages/policy-xacmlpdp-docker/pom.xml b/packages/policy-xacmlpdp-docker/pom.xml
index 20f47f6..6d2177a 100644
--- a/packages/policy-xacmlpdp-docker/pom.xml
+++ b/packages/policy-xacmlpdp-docker/pom.xml
@@ -43,6 +43,7 @@
         <docker.skip>false</docker.skip>
         <docker.skip.build>false</docker.skip.build>
         <docker.skip.push>false</docker.skip.push>
+        <docker.contextDir>${project.basedir}/src/main/docker</docker.contextDir>
         <maven.build.timestamp.format>yyyyMMdd'T'HHmm</maven.build.timestamp.format>
     </properties>
 
@@ -106,6 +107,7 @@
                             <build>
                                 <cleanup>try</cleanup>
                                 <dockerFile>${dockerFile}</dockerFile>
+                                <contextDir>${docker.contextDir}</contextDir>
                                 <tags>
                                     <tag>${project.version}</tag>
                                     <tag>${project.version}-${maven.build.timestamp}</tag>