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/boards/product/api_adapter.go

@@ -8,11 +8,11 @@ import (
 
 	"github.com/gorilla/mux"
 
-	mm_model "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/mlog"
+	"github.com/mattermost/mattermost-server/server/v8/channels/app/request"
+	mm_model "github.com/mattermost/mattermost-server/server/v8/model"
+	"github.com/mattermost/mattermost-server/server/v8/platform/shared/mlog"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/model"
+	"github.com/mattermost/mattermost-server/server/v8/boards/model"
 )
 
 // normalizeAppError returns a truly nil error if appErr is nil

server/boards/product/boards_product.go

@@ -7,13 +7,13 @@ import (
 	"errors"
 	"fmt"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/model"
-	"github.com/mattermost/mattermost-server/v6/server/boards/server"
+	"github.com/mattermost/mattermost-server/server/v8/boards/model"
+	"github.com/mattermost/mattermost-server/server/v8/boards/server"
 
-	mm_model "github.com/mattermost/mattermost-server/v6/model"
-	"github.com/mattermost/mattermost-server/v6/plugin"
-	"github.com/mattermost/mattermost-server/v6/server/channels/product"
-	"github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+	"github.com/mattermost/mattermost-server/server/v8/channels/product"
+	mm_model "github.com/mattermost/mattermost-server/server/v8/model"
+	"github.com/mattermost/mattermost-server/server/v8/platform/shared/mlog"
+	"github.com/mattermost/mattermost-server/server/v8/plugin"
 )
 
 const (

server/boards/product/imports/boards_imports.go

@@ -6,5 +6,5 @@ package imports
 import (
 	// Needed to ensure the init() method in the FocalBoard product is run.
 	// This file is copied to the mmserver imports package via makefile.
-	_ "github.com/mattermost/mattermost-server/v6/server/boards/product"
+	_ "github.com/mattermost/mattermost-server/server/v8/boards/product"
 )