new: [opensem] add `paybox-system` relation

opensem/README.org

@@ -8,3 +8,12 @@ and ~yarn.lock~ to ensure reproducible build.
 
 We provide the resulting production ready application files in a
 ~tar.xz~.
+
+* Charm usage
+
+Please note that =paylib-system= relation is required and no
+auto-summon exists. It won't auto-pair neither as no charm currently
+provides this relation.
+
+So you need to explicitly express this relation to a =stub= service.
+

opensem/hooks/paybox_system-relation-joined

@@ -0,0 +1,62 @@
+#!/bin/bash
+
+. lib/common
+
+set -e
+
+test=$(relation-get test 2>/dev/null) || true
+site=$(relation-get site) || {
+    err "The 'site' option is required."
+    exit 1
+}
+rank=$(relation-get rank) || {
+    err "The 'rank' option is required."
+    exit 1
+}
+id=$(relation-get id) || {
+    err "The 'id' option is required."
+    exit 1
+}
+hmac_key=$(relation-get hmac-key) || {
+    err "The 'hmac-key' option is required."
+    exit 1
+}
+
+[ -n "$test" ] && opensem:config-set PAYBOX_TEST "$test"
+opensem:config-set PAYBOX_SITE "$site"
+opensem:config-set PAYBOX_RANK "$rank"
+opensem:config-set PAYBOX_ID "$id"
+opensem:config-set PAYBOX_HMAC_KEY "$hmac_key"
+
+paybox_url="http://www1.paybox.com/wp-content/uploads/2014/03/pubkey.pem"
+paybox_pubkey_path="$SERVICE_DATASTORE/var/lib/opensem/paybox/pubkey.pem"
+
+if ! [ -f "$paybox_pubkey_path" ]; then
+    mkdir -p "${paybox_pubkey_path%/*}"
+    if ! curl -sSL "$paybox_url" -o "$paybox_pubkey_path"; then
+        err "Failed to download Paybox public key from $paybox_url"
+        exit 1
+    fi
+fi
+
+## and create the mount point also:
+paybox_mount_dir="$SERVICE_CONFIGSTORE/opt/apps/$SERVICE_NAME/storage/paybox"
+if ! [ -d "$paybox_mount_dir" ]; then
+    mkdir -p "$paybox_mount_dir" || {
+        err "Could not create directory $paybox_mount_dir"
+        exit 1
+    }
+fi
+
+
+php_fpm_service=$(service:traverse "$SERVICE_NAME":php-fpm) || {
+    err "Could not find php-fpm service for $SERVICE_NAME"
+    exit 1
+}
+
+config-add "
+services:
+  $php_fpm_service:
+    volumes:
+      - $SERVICE_DATASTORE/var/lib/opensem/paybox:/opt/apps/$SERVICE_NAME/storage/paybox:ro
+"

opensem/metadata.yml

@@ -74,3 +74,11 @@ uses:
     solves:
       unmanaged-logs: "in docker logs"
     #default-options:
+  paybox-system:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: required
+    auto: pair
+    solves:
+      missing-payment: "credit card payment"
+    #default-options: