PLT-3105 Files table migration (#4068)

* Implemented initial changes for files table

* Removed *_benchmark_test.go files

* Re-implemented GetPublicFile and added support for old path

* Localization for files table

* Moved file system code into utils package

* Finished server-side changes and added initial upgrade script

* Added getPostFiles api

* Re-add Extension and HasPreviewImage fields to FileInfo

* Removed unused translation

* Fixed merge conflicts left over after permissions changes

* Forced FileInfo.extension to be lower case

* Changed FileUploadResponse to contain the FileInfos instead of FileIds

* Fixed permissions on getFile* calls

* Fixed notifications for file uploads

* Added initial version of client code for files changes

* Permanently added FileIds field to Post object and removed Post.HasFiles

* Updated PostStore.Update to be usable in more circumstances

* Re-added Filenames field and switched file migration to be entirely lazy-loaded

* Increased max listener count for FileStore

* Removed unused fileInfoCache

* Moved file system code back into api

* Removed duplicate test case

* Fixed unit test running on ports other than 8065

* Renamed HasPermissionToPostContext to HasPermissionToChannelByPostContext

* Refactored handleImages to make it more easily understandable

* Renamed getPostFiles to getFileInfosForPost

* Re-added pre-FileIds posts to analytics

* Changed files to be saved as their ids as opposed to id/filename.ext

* Renamed FileInfo.UserId to FileInfo.CreatorId

* Fixed detection of language in CodePreview

* Fixed switching between threads in the RHS not loading new files

* Add serverside protection against a rare bug where the client sends the same file twice for a single post

* Refactored the important parts of uploadFile api call into a function that can be called without a web context

model/post.go

@@ -35,7 +35,8 @@ type Post struct {
 	Type          string          `json:"type"`
 	Props         StringInterface `json:"props"`
 	Hashtags      string          `json:"hashtags"`
-	Filenames     StringArray     `json:"filenames"`
+	Filenames     StringArray     `json:"filenames,omitempty"` // Deprecated, do not use this field any more
+	FileIds       StringArray     `json:"file_ids,omitempty"`
 	PendingPostId string          `json:"pending_post_id" db:"-"`
 }
 
@@ -118,6 +119,10 @@ func (o *Post) IsValid() *AppError {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.filenames.app_error", nil, "id="+o.Id)
 	}
 
+	if utf8.RuneCountInString(ArrayToJson(o.FileIds)) > 150 {
+		return NewLocAppError("Post.IsValid", "model.post.is_valid.file_ids.app_error", nil, "id="+o.Id)
+	}
+
 	if utf8.RuneCountInString(StringInterfaceToJson(o.Props)) > 8000 {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.props.app_error", nil, "id="+o.Id)
 	}
@@ -145,15 +150,16 @@ func (o *Post) PreSave() {
 	if o.Filenames == nil {
 		o.Filenames = []string{}
 	}
+
+	if o.FileIds == nil {
+		o.FileIds = []string{}
+	}
 }
 
 func (o *Post) MakeNonNil() {
 	if o.Props == nil {
 		o.Props = make(map[string]interface{})
 	}
-	if o.Filenames == nil {
-		o.Filenames = []string{}
-	}
 }
 
 func (o *Post) AddProp(key string, value interface{}) {