feat: add postgres php modules

adds postgres headers and the php modules for pdo_pgsql so you can run
nextcloud with a postgres database backend

webservice/Dockerfile

@@ -25,6 +25,7 @@ RUN \
         libjpeg-dev \
         libgmp-dev \
         curl \
+        libpq-dev \
         cron && \
     apt-get clean && \
 	rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
@@ -61,7 +62,9 @@ RUN \
         bcmath \
         sysvsem \
         pcntl \
-        opcache && \
+        opcache \
+        pdo_pgsql \
+        pdo && \
     CFLAGS="-I/usr/src/php" docker-php-ext-install xmlreader
 
 RUN \