[MM-26812] Add support for resumable file uploads (#15252)

* Implement AppendFile for FileBackend

* Split test into subtests

* [MM-26812] Add support for resumable file uploads (#15252)

* Implement UploadSession

* Implement UploadSessionStore

* Add error strings

* Implement resumable file uploads

* Add UploadType

* Fix retry layer tests

* Regenerate store layers

* Fix store error handling

* Use base for filename

* Prevent concurrent uploads on the same upload session

* Fix erroneus error string

* Improve error handling

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

* Fix translations

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/app_iface.go

@@ -360,6 +360,7 @@ type AppIface interface {
 	AddUserToTeamByToken(userId string, tokenId string) (*model.Team, *model.AppError)
 	AdjustImage(file io.Reader) (*bytes.Buffer, *model.AppError)
 	AllowOAuthAppAccessToUser(userId string, authRequest *model.AuthorizeRequest) (string, *model.AppError)
+	AppendFile(fr io.Reader, path string) (int64, *model.AppError)
 	AsymmetricSigningKey() *ecdsa.PrivateKey
 	AttachDeviceId(sessionId string, deviceId string, expiresAt int64) *model.AppError
 	AttachSessionCookies(w http.ResponseWriter, r *http.Request)
@@ -427,6 +428,7 @@ type AppIface interface {
 	CreateTeam(team *model.Team) (*model.Team, *model.AppError)
 	CreateTeamWithUser(team *model.Team, userId string) (*model.Team, *model.AppError)
 	CreateTermsOfService(text, userId string) (*model.TermsOfService, *model.AppError)
+	CreateUploadSession(us *model.UploadSession) (*model.UploadSession, *model.AppError)
 	CreateUserAccessToken(token *model.UserAccessToken) (*model.UserAccessToken, *model.AppError)
 	CreateUserAsAdmin(user *model.User, redirect string) (*model.User, *model.AppError)
 	CreateUserFromSignup(user *model.User, redirect string) (*model.User, *model.AppError)
@@ -670,6 +672,8 @@ type AppIface interface {
 	GetTeamsForUser(userId string) ([]*model.Team, *model.AppError)
 	GetTeamsUnreadForUser(excludeTeamId string, userId string) ([]*model.TeamUnread, *model.AppError)
 	GetTermsOfService(id string) (*model.TermsOfService, *model.AppError)
+	GetUploadSession(uploadId string) (*model.UploadSession, *model.AppError)
+	GetUploadSessionsForUser(userId string) ([]*model.UploadSession, *model.AppError)
 	GetUser(userId string) (*model.User, *model.AppError)
 	GetUserAccessToken(tokenId string, sanitize bool) (*model.UserAccessToken, *model.AppError)
 	GetUserAccessTokens(page, perPage int) ([]*model.UserAccessToken, *model.AppError)
@@ -980,6 +984,7 @@ type AppIface interface {
 	UpdateUserAuth(userId string, userAuth *model.UserAuth) (*model.UserAuth, *model.AppError)
 	UpdateUserNotifyProps(userId string, props map[string]string) (*model.User, *model.AppError)
 	UpdateUserRoles(userId string, newRoles string, sendWebSocketEvent bool) (*model.User, *model.AppError)
+	UploadData(us *model.UploadSession, rd io.Reader) (*model.FileInfo, *model.AppError)
 	UploadEmojiImage(id string, imageData *multipart.FileHeader) *model.AppError
 	UploadMultipartFiles(teamId string, channelId string, userId string, fileHeaders []*multipart.FileHeader, clientIds []string, now time.Time) (*model.FileUploadResponse, *model.AppError)
 	UpsertGroupMember(groupID string, userID string) (*model.GroupMember, *model.AppError)