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/channels/product/README.md

@@ -17,7 +17,7 @@ type Product interface {
 }
 ```
 
-The `app.Server` will take care of starting and stopping products. The product shall register itself via a function called `RegisterProduct` provided by `github.com/mattermost/mattermost-server/v6/server/app` package. To register a product,
+The `app.Server` will take care of starting and stopping products. The product shall register itself via a function called `RegisterProduct` provided by `github.com/mattermost/mattermost-server/server/v8/channels/app` package. To register a product,
 a product initializer is required. The signature of a product initializer is defined as following:
 
 ```Go

server/channels/product/api.go

@@ -8,12 +8,12 @@ import (
 
 	"github.com/gorilla/mux"
 
-	"github.com/mattermost/mattermost-server/v6/model"
-	"github.com/mattermost/mattermost-server/v6/server/channels/app/request"
-	"github.com/mattermost/mattermost-server/v6/server/platform/shared/filestore"
-	"github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+	"github.com/mattermost/mattermost-server/server/v8/channels/app/request"
+	"github.com/mattermost/mattermost-server/server/v8/model"
+	"github.com/mattermost/mattermost-server/server/v8/platform/shared/filestore"
+	"github.com/mattermost/mattermost-server/server/v8/platform/shared/mlog"
 
-	fb_model "github.com/mattermost/mattermost-server/v6/server/boards/model"
+	fb_model "github.com/mattermost/mattermost-server/server/v8/boards/model"
 )
 
 // RouterService enables registering the product router to the server. After registering the

server/channels/product/hooks.go

@@ -7,8 +7,8 @@ import (
 	"sync"
 	"time"
 
-	"github.com/mattermost/mattermost-server/v6/plugin"
-	"github.com/mattermost/mattermost-server/v6/server/channels/einterfaces"
+	"github.com/mattermost/mattermost-server/server/v8/channels/einterfaces"
+	"github.com/mattermost/mattermost-server/server/v8/plugin"
 )
 
 type HooksManager struct {