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

webapp/utils/utils.jsx

@@ -413,8 +413,8 @@ export function getFileType(extin) {
     return 'other';
 }
 
-export function getPreviewImagePathForFileType(fileTypeIn) {
-    var fileType = fileTypeIn.toLowerCase();
+export function getFileIconPath(fileInfo) {
+    const fileType = getFileType(fileInfo.extension);
 
     var icon;
     if (fileType in Constants.ICON_FROM_TYPE) {
@@ -451,19 +451,6 @@ export function splitFileLocation(fileLocation) {
     return {ext, name: filename, path: filePath};
 }
 
-export function getPreviewImagePath(filename) {
-    // Returns the path to a preview image that can be used to represent a file.
-    const fileInfo = splitFileLocation(filename);
-    const fileType = getFileType(fileInfo.ext);
-
-    if (fileType === 'image') {
-        return getFileUrl(fileInfo.path + '_preview.jpg');
-    }
-
-    // only images have proper previews, so just use a placeholder icon for non-images
-    return getPreviewImagePathForFileType(fileType);
-}
-
 export function toTitleCase(str) {
     function doTitleCase(txt) {
         return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();