Chore: Add test radius dockerfile

test/test-radius.dockerfile

@@ -0,0 +1,13 @@
+# Container running a test radius server
+# More instructions in https://github.com/louislam/uptime-kuma/pull/1635
+
+FROM freeradius/freeradius-server:latest
+
+RUN mkdir -p /etc/raddb/mods-config/files/
+
+RUN echo "client net {"                 > /etc/raddb/clients.conf
+RUN echo "    ipaddr = 172.17.0.0/16"  >> /etc/raddb/clients.conf
+RUN echo "    secret = testing123"     >> /etc/raddb/clients.conf
+RUN echo "}"                           >> /etc/raddb/clients.conf
+
+RUN echo "bob Cleartext-Password := \"testpw\"" > /etc/raddb/mods-config/files/authorize