v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/plugin/scheduler/scheduler.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package scheduler
+
+import (
+	"time"
+
+	"github.com/mattermost/mattermost-server/server/v8/channels/jobs"
+	"github.com/mattermost/mattermost-server/server/v8/model"
+)
+
+const schedFreq = 24 * time.Hour
+
+func MakeScheduler(jobServer *jobs.JobServer) model.Scheduler {
+	isEnabled := func(cfg *model.Config) bool {
+		return true
+	}
+	return jobs.NewPeriodicScheduler(jobServer, model.JobTypePlugins, schedFreq, isEnabled)
+}

server/plugin/scheduler/worker.go

@@ -0,0 +1,104 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package scheduler
+
+import (
+	"github.com/mattermost/mattermost-server/server/v8/channels/jobs"
+	"github.com/mattermost/mattermost-server/server/v8/model"
+	"github.com/mattermost/mattermost-server/server/v8/platform/shared/mlog"
+)
+
+type AppIface interface {
+	DeleteAllExpiredPluginKeys() *model.AppError
+}
+
+type Worker struct {
+	name      string
+	stop      chan bool
+	stopped   chan bool
+	jobs      chan model.Job
+	jobServer *jobs.JobServer
+	app       AppIface
+}
+
+func MakeWorker(jobServer *jobs.JobServer, app AppIface) model.Worker {
+	worker := Worker{
+		name:      "Plugins",
+		stop:      make(chan bool, 1),
+		stopped:   make(chan bool, 1),
+		jobs:      make(chan model.Job),
+		jobServer: jobServer,
+		app:       app,
+	}
+
+	return &worker
+}
+
+func (worker *Worker) Run() {
+	mlog.Debug("Worker started", mlog.String("worker", worker.name))
+
+	defer func() {
+		mlog.Debug("Worker finished", mlog.String("worker", worker.name))
+		worker.stopped <- true
+	}()
+
+	for {
+		select {
+		case <-worker.stop:
+			mlog.Debug("Worker received stop signal", mlog.String("worker", worker.name))
+			return
+		case job := <-worker.jobs:
+			mlog.Debug("Worker received a new candidate job.", mlog.String("worker", worker.name))
+			worker.DoJob(&job)
+		}
+	}
+}
+
+func (worker *Worker) Stop() {
+	mlog.Debug("Worker stopping", mlog.String("worker", worker.name))
+	worker.stop <- true
+	<-worker.stopped
+}
+
+func (worker *Worker) JobChannel() chan<- model.Job {
+	return worker.jobs
+}
+
+func (worker *Worker) IsEnabled(cfg *model.Config) bool {
+	return true
+}
+
+func (worker *Worker) DoJob(job *model.Job) {
+	if claimed, err := worker.jobServer.ClaimJob(job); err != nil {
+		mlog.Info("Worker experienced an error while trying to claim job",
+			mlog.String("worker", worker.name),
+			mlog.String("job_id", job.Id),
+			mlog.String("error", err.Error()))
+		return
+	} else if !claimed {
+		return
+	}
+
+	if err := worker.app.DeleteAllExpiredPluginKeys(); err != nil {
+		mlog.Error("Worker: Failed to delete expired keys", mlog.String("worker", worker.name), mlog.String("job_id", job.Id), mlog.String("error", err.Error()))
+		worker.setJobError(job, err)
+		return
+	}
+
+	mlog.Info("Worker: Job is complete", mlog.String("worker", worker.name), mlog.String("job_id", job.Id))
+	worker.setJobSuccess(job)
+}
+
+func (worker *Worker) setJobSuccess(job *model.Job) {
+	if err := worker.jobServer.SetJobSuccess(job); err != nil {
+		mlog.Error("Worker: Failed to set success for job", mlog.String("worker", worker.name), mlog.String("job_id", job.Id), mlog.String("error", err.Error()))
+		worker.setJobError(job, err)
+	}
+}
+
+func (worker *Worker) setJobError(job *model.Job, appError *model.AppError) {
+	if err := worker.jobServer.SetJobError(job, appError); err != nil {
+		mlog.Error("Worker: Failed to set job error", mlog.String("worker", worker.name), mlog.String("job_id", job.Id), mlog.String("error", err.Error()))
+	}
+}