[MM-63556] mmctl: Add compliance export download cmd (#30576)

* add mmctl compliance export download command and tests

- Introduced `ComplianceExportDownloadCmd` to facilitate downloading compliance export files.
- Implemented the `DownloadComplianceExport` method in the Client interface for handling file downloads.
- Added unit tests for the download command, covering successful downloads, error handling for non-existent jobs, and retries on failure.
- Included end-to-end tests to validate the command's functionality.
- Updated documentation to include usage examples and options for the new command.

* don't know why this was left out

* PR comments

* adjust test for new retry logic

* refactored download fn for compliance_export and export

* fix test due to fixed logic

* docs

server/public/model/client4.go

@@ -1512,6 +1512,7 @@ func (c *Client4) GetUsersByIdsWithOptions(ctx context.Context, userIds []string
 		return nil, BuildResponse(r), err
 	}
 	defer closeBody(r)
+
 	var list []*User
 	if err := json.NewDecoder(r.Body).Decode(&list); err != nil {
 		return nil, nil, NewAppError("GetUsersByIdsWithOptions", "api.unmarshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
@@ -3207,7 +3208,7 @@ func (c *Client4) PatchChannel(ctx context.Context, channelId string, patch *Cha
 	var ch *Channel
 	err = json.NewDecoder(r.Body).Decode(&ch)
 	if err != nil {
-		return nil, BuildResponse(r), NewAppError("PatchChannel", "api.marshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
+		return nil, BuildResponse(r), NewAppError("PatchChannel", "api.unmarshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
 	}
 	return ch, BuildResponse(r), nil
 }
@@ -8927,6 +8928,31 @@ func (c *Client4) GetUserThreads(ctx context.Context, userId, teamId string, opt
 	return &threads, BuildResponse(r), nil
 }
 
+func (c *Client4) DownloadComplianceExport(ctx context.Context, jobId string, wr io.Writer) (string, error) {
+	r, err := c.DoAPIGet(ctx, c.jobsRoute()+fmt.Sprintf("/%s/download", jobId), "")
+	if err != nil {
+		return "", err
+	}
+	defer closeBody(r)
+
+	// Try to get the filename from the Content-Disposition header
+	var filename string
+	if cd := r.Header.Get("Content-Disposition"); cd != "" {
+		var params map[string]string
+		if _, params, err = mime.ParseMediaType(cd); err == nil {
+			if params["filename"] != "" {
+				filename = params["filename"]
+			}
+		}
+	}
+
+	_, err = io.Copy(wr, r.Body)
+	if err != nil {
+		return filename, NewAppError("DownloadComplianceExport", "model.client.copy.app_error", nil, "", r.StatusCode).Wrap(err)
+	}
+	return filename, nil
+}
+
 func (c *Client4) GetUserThread(ctx context.Context, userId, teamId, threadId string, extended bool) (*ThreadResponse, *Response, error) {
 	url := c.userThreadRoute(userId, teamId, threadId)
 	if extended {