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/model/migration.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+const (
+	AdvancedPermissionsMigrationKey       = "AdvancedPermissionsMigrationComplete"
+	MigrationKeyAdvancedPermissionsPhase2 = "migration_advanced_permissions_phase_2"
+
+	MigrationKeyEmojiPermissionsSplit                  = "emoji_permissions_split"
+	MigrationKeyWebhookPermissionsSplit                = "webhook_permissions_split"
+	MigrationKeyListJoinPublicPrivateTeams             = "list_join_public_private_teams"
+	MigrationKeyRemovePermanentDeleteUser              = "remove_permanent_delete_user"
+	MigrationKeyAddBotPermissions                      = "add_bot_permissions"
+	MigrationKeyApplyChannelManageDeleteToChannelUser  = "apply_channel_manage_delete_to_channel_user"
+	MigrationKeyRemoveChannelManageDeleteFromTeamUser  = "remove_channel_manage_delete_from_team_user"
+	MigrationKeyViewMembersNewPermission               = "view_members_new_permission"
+	MigrationKeyAddManageGuestsPermissions             = "add_manage_guests_permissions"
+	MigrationKeyChannelModerationsPermissions          = "channel_moderations_permissions"
+	MigrationKeyAddUseGroupMentionsPermission          = "add_use_group_mentions_permission"
+	MigrationKeyAddSystemConsolePermissions            = "add_system_console_permissions"
+	MigrationKeySidebarCategoriesPhase2                = "migration_sidebar_categories_phase_2"
+	MigrationKeyAddConvertChannelPermissions           = "add_convert_channel_permissions"
+	MigrationKeyAddSystemRolesPermissions              = "add_system_roles_permissions"
+	MigrationKeyAddBillingPermissions                  = "add_billing_permissions"
+	MigrationKeyAddManageSharedChannelPermissions      = "manage_shared_channel_permissions"
+	MigrationKeyAddManageSecureConnectionsPermissions  = "manage_secure_connections_permissions"
+	MigrationKeyAddDownloadComplianceExportResults     = "download_compliance_export_results"
+	MigrationKeyAddComplianceSubsectionPermissions     = "compliance_subsection_permissions"
+	MigrationKeyAddExperimentalSubsectionPermissions   = "experimental_subsection_permissions"
+	MigrationKeyAddAuthenticationSubsectionPermissions = "authentication_subsection_permissions"
+	MigrationKeyAddSiteSubsectionPermissions           = "site_subsection_permissions"
+	MigrationKeyAddEnvironmentSubsectionPermissions    = "environment_subsection_permissions"
+	MigrationKeyAddReportingSubsectionPermissions      = "reporting_subsection_permissions"
+	MigrationKeyAddTestEmailAncillaryPermission        = "test_email_ancillary_permission"
+	MigrationKeyAddAboutSubsectionPermissions          = "about_subsection_permissions"
+	MigrationKeyAddIntegrationsSubsectionPermissions   = "integrations_subsection_permissions"
+	MigrationKeyAddPlaybooksPermissions                = "playbooks_permissions"
+	MigrationKeyAddCustomUserGroupsPermissions         = "custom_groups_permissions"
+	MigrationKeyAddPlayboosksManageRolesPermissions    = "playbooks_manage_roles"
+	MigrationKeyAddProductsBoardsPermissions           = "products_boards"
+	MigrationKeyAddCustomUserGroupsPermissionRestore   = "custom_groups_permission_restore"
+)