L2SS-685: Explicitly provide alerta configuration files

docker-compose/alerta-web/Dockerfile

 FROM alerta/alerta-web
 
+COPY alertad.conf /app/alertad.conf
+COPY alerta.conf /app/alerta.conf
+COPY config.json /web/config.json
+
 RUN pip install git+https://github.com/alerta/alerta-contrib.git#subdirectory=plugins/slack
+

docker-compose/alerta-web/alerta.conf

+[DEFAULT]
+sslverify = no
+output = presto
+endpoint = http://localhost:8080/api
+timezone = Europe/London
+key = NpzX0z_fX8TVKZtXpzop-pi2MhaGnLawKVqbJBoA
+debug = yes

docker-compose/alerta-web/alertad.conf

+DEBUG = True
+SECRET = "T=&7xvF2S&x7w_JAcq$h1x5ocfA)8H2i"
+
+PLUGINS = ['reject', 'blackout', 'normalise', 'enhance', 'slack']

docker-compose/alerta-web/config.json

+{"endpoint": "/api"}