Merge pull request juju#17919 from amandahla/add-charm-rev-status

juju#17919

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With this change will be possible get the revision from an Application.

Note: I'm targeting 3.1 since per CONTRIBUTING it should be targeted at the lowest version affected. Please let me know if a different one should be targeted instead.

## Checklist

<!-- If an item is not applicable, use `~strikethrough~`. -->
- [x] Code style: imports ordered, good names, simple structure, etc
- [ ] Comments saying why design decisions were made
- [ ] Go unit tests, with comments saying what you're testing
- [ ] [Integration tests](https://github.com/juju/juju/tree/main/tests), with comments saying what you're testing
- [ ] [doc.go](https://discourse.charmhub.io/t/readme-in-packages/451) added or updated in changed packages

## QA steps

While creating a third-party client, is possible to get charm revision like this:
```
func (r *registry) parseStatus(status *params.FullStatus) {
 for applicationName, application := range status.Applications {
 r.jujuApplications.With(prometheus.Labels{
 "name": applicationName,
 "status": application.Status.Status,
 "channel": application.CharmChannel,
 "revision": application.CharmRev,
 }).Set(checkStatus(application.Status.Status, []string{"active"}))
...
```

## Documentation changes

No changes.

## Links

To be used in https://github.com/neoaggelos/juju_exporter

**Launchpad bug:** https://bugs.launchpad.net/juju/+bug/

**Jira card:** JUJU-

apiserver/facades/client/client/api_test.go

@@ -193,8 +193,9 @@ var scenarioStatus = &params.FullStatus{
 	},
 	Applications: map[string]params.ApplicationStatus{
 		"logging": {
-			Charm: "local:quantal/logging-1",
-			Base:  params.Base{Name: "ubuntu", Channel: "12.10/stable"},
+			Charm:    "local:quantal/logging-1",
+			CharmRev: 1,
+			Base:     params.Base{Name: "ubuntu", Channel: "12.10/stable"},
 			Relations: map[string][]string{
 				"logging-directory": {"wordpress"},
 			},
@@ -212,6 +213,7 @@ var scenarioStatus = &params.FullStatus{
 		},
 		"mysql": {
 			Charm:         "local:quantal/mysql-1",
+			CharmRev:      1,
 			Base:          params.Base{Name: "ubuntu", Channel: "12.10/stable"},
 			Relations:     map[string][]string{},
 			SubordinateTo: []string{},
@@ -229,8 +231,9 @@ var scenarioStatus = &params.FullStatus{
 			},
 		},
 		"wordpress": {
-			Charm: "local:quantal/wordpress-3",
-			Base:  params.Base{Name: "ubuntu", Channel: "12.10/stable"},
+			Charm:    "local:quantal/wordpress-3",
+			CharmRev: 3,
+			Base:     params.Base{Name: "ubuntu", Channel: "12.10/stable"},
 			Relations: map[string][]string{
 				"logging-dir": {"logging"},
 			},

apiserver/facades/client/client/status.go

@@ -1392,6 +1392,7 @@ func (context *statusContext) processApplication(application *state.Application)
 		Charm:        applicationCharm.URL(),
 		CharmVersion: applicationCharm.Version(),
 		CharmProfile: charmProfileName,
+		CharmRev:     applicationCharm.Revision(),
 		CharmChannel: channel,
 		Base: params.Base{
 			Name:    base.OS,

apiserver/facades/client/client/status_test.go

@@ -1124,12 +1124,15 @@ func (s *CAASStatusSuite) TestStatusCloudContainerSet(c *gc.C) {
 
 func (s *CAASStatusSuite) assertUnitStatus(c *gc.C, appStatus params.ApplicationStatus, status, info string) {
 	curl, _ := s.app.CharmURL()
+	parsedCurl, err := charm.ParseURL(*curl)
+	c.Assert(err, jc.ErrorIsNil)
 	workloadVersion := ""
 	if info != "installing agent" && info != "blocked" {
 		workloadVersion = "gitlab/latest"
 	}
 	c.Assert(appStatus, jc.DeepEquals, params.ApplicationStatus{
 		Charm:           *curl,
+		CharmRev:        parsedCurl.Revision,
 		Base:            params.Base{Name: "ubuntu", Channel: "20.04/stable"},
 		WorkloadVersion: workloadVersion,
 		Relations:       map[string][]string{},

apiserver/facades/schema.json

@@ -16238,6 +16238,9 @@
                         "charm-profile": {
                             "type": "string"
                         },
+                        "charm-rev": {
+                            "type": "integer"
+                        },
                         "charm-version": {
                             "type": "string"
                         },

rpc/params/status.go

@@ -147,6 +147,7 @@ type ApplicationStatus struct {
 	CharmVersion     string                     `json:"charm-version"`
 	CharmProfile     string                     `json:"charm-profile"`
 	CharmChannel     string                     `json:"charm-channel,omitempty"`
+	CharmRev         int                        `json:"charm-rev,omitempty"`
 	Base             Base                       `json:"base"`
 	Exposed          bool                       `json:"exposed"`
 	ExposedEndpoints map[string]ExposedEndpoint `json:"exposed-endpoints,omitempty"`