Revert "Remove Prometheus charm"

This reverts commit 722b50279283ef22a9f9fab256e416f795427f26.

Reason for revert: Grafana-k8s requires Juju 3.1 and we are not ready
to change Juju versions at this time

Change-Id: Ibc17a6973c981a21152a8f74c8054e42ac21b24f
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/installers/charm/prometheus/metadata.yaml b/installers/charm/prometheus/metadata.yaml
new file mode 100644
index 0000000..932ccc2
--- /dev/null
+++ b/installers/charm/prometheus/metadata.yaml
@@ -0,0 +1,51 @@
+# Copyright 2021 Canonical Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+# For those usages not covered by the Apache License, Version 2.0 please
+# contact: legal@canonical.com
+#
+# To get in touch with the maintainers, please contact:
+# osm-charmers@lists.launchpad.net
+##
+
+name: osm-prometheus
+summary: OSM Prometheus
+description: |
+  A CAAS charm to deploy OSM's Prometheus.
+series:
+  - kubernetes
+tags:
+  - kubernetes
+  - osm
+  - prometheus
+min-juju-version: 2.8.0
+deployment:
+  type: stateful
+  service: cluster
+resources:
+  backup-image:
+    type: oci-image
+    description: Container image to run backup actions
+    upstream-source: "ed1000/prometheus-backup:latest"
+  image:
+    type: oci-image
+    description: OSM docker image for Prometheus
+    upstream-source: "ubuntu/prometheus:latest"
+provides:
+  prometheus:
+    interface: prometheus
+storage:
+  data:
+    type: filesystem
+    location: /prometheus