Merge pull request #1 from canonical/kf-4450-feat-metacontroller-rock

# Description

`metacontroller` container image should be converted to ROCK.
This PR contains initial ROCK implementation based on best practices.

# Summary of changes:
- Initial ROCK based on the same version of source code as upstream container.

# Scan results:

ROCK image `metacontroller:2.0.4_22.04_1`
CRITICAL: 0 HIGH: 14 MED: 6 LOW: 0

As compared to upstream image `metacontroller:2.0.4`
CRITICAL: 3 HIGH: 41 MED: 11 LOW: 0

# Testing

Manual testing was performed. See the log below.

<details><summary>Manual test log</summary>

```
$ docker run charmedkubeflow/metacontroller:2.0.4_22.04_1 exec pebble start metacontroller
2023-09-26T15:48:59.689Z [pebble] Started daemon.
2023-09-26T15:48:59.710Z [pebble] POST /v1/exec 20.143166ms 202
2023-09-26T15:48:59.727Z [pebble] GET /v1/tasks/1/websocket/control 16.942361ms 200
2023-09-26T15:48:59.727Z [pebble] GET /v1/tasks/1/websocket/stdio 62.045µs 200
2023-09-26T15:48:59.727Z [pebble] GET /v1/tasks/1/websocket/stderr 85.937µs 200
2023-09-26T15:48:59.768Z [pebble] POST /v1/services 27.166079ms 202
2023-09-26T15:48:59.768Z [pebble] Service "metacontroller" starting: metacontroller
2023-09-26T15:48:59.779Z [metacontroller] {"level":"info","ts":1695743339.779103,"msg":"Discovery cache flush interval","discovery_interval":30}
2023-09-26T15:48:59.779Z [metacontroller] {"level":"info","ts":1695743339.7791352,"msg":"API server object cache flush interval","cache_flush_interval":1800}
2023-09-26T15:48:59.779Z [metacontroller] {"level":"info","ts":1695743339.7791398,"msg":"Metrics http server address","port":":9999"}
2023-09-26T15:48:59.779Z [metacontroller] {"level":"info","ts":1695743339.7791443,"msg":"Metacontroller build information","version":"dev"}
2023-09-26T15:48:59.779Z [metacontroller] {"level":"error","ts":1695743339.7792091,"msg":"Terminating","error":"invalid configuration: no configuration has been provided, try setting KUBERNETES_MASTER environment variable","errorCauses":[{"error":"no configuration has been provided, try setting KUBERNETES_MASTER environment variable"}],"stacktrace":"runtime.main\n\t/snap/go/9362/src/runtime/proc.go:225"}
error: cannot perform the following tasks:
- Start service "metacontroller" (cannot start service: exited quickly with code 1)
2023-09-26T15:48:59.905Z [pebble] GET /v1/changes/1/wait 176.788211ms 200
```

</details>

rockcraft.yaml

@@ -0,0 +1,43 @@
+# Based on https://github.com/metacontroller/metacontroller/blob/v2.0.4/Dockerfile
+name: metacontroller
+summary: Metacontroller in a ROCK.
+description: "Metacontroller  is an add-on for Kubernetes that makes it easy to write and deploy custom controllers in the form of simple scripts."
+version: "2.0.4_22.04_1"
+license: Apache-2.0
+build-base: ubuntu:22.04
+base: bare
+run-user: _daemon_
+services:
+  metacontroller:
+    command: metacontroller
+    working-dir: /usr/bin
+    override: replace
+    startup: enabled
+platforms:
+  amd64:
+
+parts:
+  metacontroller:
+    plugin: go
+    source: https://github.com/metacontroller/metacontroller
+    source-type: git
+    source-tag: "v2.0.4"
+    build-snaps:
+      - go/1.16/stable
+    build-environment:
+      - CGO_ENABLED: 0
+    stage-packages:
+      - ca-certificates
+    override-build: |
+      make install
+      mkdir -p ${CRAFT_PART_INSTALL}/usr/bin
+      install -D ${CRAFT_PART_INSTALL}/bin/metacontroller ${CRAFT_PART_INSTALL}/usr/bin
+
+  security-team-requirement:
+    plugin: nil
+    override-build: |
+      # security requirement
+      # there are no packages installed in `bare` base which is used in this rock
+      mkdir -p ${CRAFT_PART_INSTALL}/usr/share/rocks
+      (echo "# os-release" && cat /etc/os-release && echo "# dpkg-query") \
+       > ${CRAFT_PART_INSTALL}/usr/share/rocks/dpkg.query