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/upload_session.go

@@ -0,0 +1,127 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// UploadType defines the type of an upload.
+type UploadType string
+
+const (
+	UploadTypeAttachment   UploadType = "attachment"
+	UploadTypeImport       UploadType = "import"
+	IncompleteUploadSuffix            = ".tmp"
+)
+
+// UploadNoUserID is a "fake" user id used by the API layer when in local mode.
+const UploadNoUserID = "nouser"
+
+// UploadSession contains information used to keep track of a file upload.
+type UploadSession struct {
+	// The unique identifier for the session.
+	Id string `json:"id"`
+	// The type of the upload.
+	Type UploadType `json:"type"`
+	// The timestamp of creation.
+	CreateAt int64 `json:"create_at"`
+	// The id of the user performing the upload.
+	UserId string `json:"user_id"`
+	// The id of the channel to upload to.
+	ChannelId string `json:"channel_id,omitempty"`
+	// The name of the file to upload.
+	Filename string `json:"filename"`
+	// The path where the file is stored.
+	Path string `json:"-"`
+	// The size of the file to upload.
+	FileSize int64 `json:"file_size"`
+	// The amount of received data in bytes. If equal to FileSize it means the
+	// upload has finished.
+	FileOffset int64 `json:"file_offset"`
+	// Id of remote cluster if uploading for shared channel
+	RemoteId string `json:"remote_id"`
+	// Requested file id if uploading for shared channel
+	ReqFileId string `json:"req_file_id"`
+}
+
+func (us *UploadSession) Auditable() map[string]interface{} {
+	return map[string]interface{}{
+		"id":         us.Id,
+		"type":       us.Type,
+		"user_id":    us.UserId,
+		"channel_id": us.ChannelId,
+		"filename":   us.Filename,
+		"file_size":  us.FileSize,
+		"remote_id":  us.RemoteId,
+		"ReqFileId":  us.ReqFileId,
+	}
+}
+
+// PreSave is a utility function used to fill required information.
+func (us *UploadSession) PreSave() {
+	if us.Id == "" {
+		us.Id = NewId()
+	}
+
+	if us.CreateAt == 0 {
+		us.CreateAt = GetMillis()
+	}
+}
+
+// IsValid validates an UploadType. It returns an error in case of
+// failure.
+func (t UploadType) IsValid() error {
+	switch t {
+	case UploadTypeAttachment:
+		return nil
+	case UploadTypeImport:
+		return nil
+	default:
+	}
+	return fmt.Errorf("invalid UploadType %s", t)
+}
+
+// IsValid validates an UploadSession. It returns an error in case of
+// failure.
+func (us *UploadSession) IsValid() *AppError {
+	if !IsValidId(us.Id) {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.id.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	if err := us.Type.IsValid(); err != nil {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.type.app_error", nil, "", http.StatusBadRequest).Wrap(err)
+	}
+
+	if !IsValidId(us.UserId) && us.UserId != UploadNoUserID {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.user_id.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	if us.Type == UploadTypeAttachment && !IsValidId(us.ChannelId) {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.channel_id.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	if us.CreateAt == 0 {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.create_at.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	if us.Filename == "" {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.filename.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	if us.FileSize <= 0 {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.file_size.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	if us.FileOffset < 0 || us.FileOffset > us.FileSize {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.file_offset.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	if us.Path == "" {
+		return NewAppError("UploadSession.IsValid", "model.upload_session.is_valid.path.app_error", nil, "id="+us.Id, http.StatusBadRequest)
+	}
+
+	return nil
+}