MM-43918: freemium limit for storage (#20225)

Summary
Adds an API end point to return storage usage

Ticket Link
https://mattermost.atlassian.net/browse/MM-43918

model/client4.go

@@ -8122,7 +8122,20 @@ func (c *Client4) GetPostsUsage() (*PostsUsage, *Response, error) {
 	return usage, BuildResponse(r), err
 }
 
-// GetTeamsUsage returns total usage of teams for the instance
+// GetStorageUsage returns the file storage usage for the instance,
+// rounded down the most signigicant digit
+func (c *Client4) GetStorageUsage() (*StorageUsage, *Response, error) {
+	r, err := c.DoAPIGet(c.usageRoute()+"/storage", "")
+	if err != nil {
+		return nil, BuildResponse(r), err
+	}
+	defer closeBody(r)
+
+	var usage *StorageUsage
+	err = json.NewDecoder(r.Body).Decode(&usage)
+	return usage, BuildResponse(r), err
+}
+
 // GetTeamsUsage returns total usage of teams for the instance
 func (c *Client4) GetTeamsUsage() (*TeamsUsage, *Response, error) {
 	r, err := c.DoAPIGet(c.usageRoute()+"/teams", "")

model/usage.go

@@ -7,6 +7,10 @@ type PostsUsage struct {
 	Count int64 `json:"count"`
 }
 
+type StorageUsage struct {
+	Bytes int64 `json:"bytes"`
+}
+
 type TeamsUsage struct {
 	Active        int64 `json:"active"`
 	CloudArchived int64 `json:"cloud_archived"`