MM-17912: Allow searching for files through plugin API (#13647)

* constants and options for getting files

* Method to get files with options

* Add i18n strings for en

* Add API methods for getting files with options

* gofmt -s file

* explicitly set create at in tests

* use greater than nanosecond time difference for tests

* use gte instead of gt for getting files by created time

* use created at time as default sort order for getting file infos

* use explicit inline strings instead of format strings

* join tables only when required

* use if as secondary sort, and update tests

* update field docs to reflect previous changes

* make page and perPage get options as required

* add json struct tags to GetFileOptions

* bump minimum server versioni

* remove sorting by username and channelname

* use bool for sort order type

* use FileInfo prefix instead of just File

* clearer comments

* use zero-based page numbering

* test filtering by user and channel

* remove unnecessary whitespace

* use int instead of uint for page and perPage arguments

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

app/plugin_api.go

@@ -567,6 +567,10 @@ func (api *PluginAPI) GetFileInfo(fileId string) (*model.FileInfo, *model.AppErr
 	return api.app.GetFileInfo(fileId)
 }
 
+func (api *PluginAPI) GetFileInfos(page, perPage int, opt *model.GetFileInfosOptions) ([]*model.FileInfo, *model.AppError) {
+	return api.app.GetFileInfos(page, perPage, opt)
+}
+
 func (api *PluginAPI) GetFileLink(fileId string) (string, *model.AppError) {
 	if !*api.app.Config().FileSettings.EnablePublicLink {
 		return "", model.NewAppError("GetFileLink", "plugin_api.get_file_link.disabled.app_error", nil, "", http.StatusNotImplemented)