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>

plugin/api.go

@@ -659,6 +659,12 @@ type API interface {
 	// Minimum server version: 5.3
 	GetFileInfo(fileId string) (*model.FileInfo, *model.AppError)
 
+	// GetFileInfos gets File Infos with options
+	//
+	// @tag File
+	// Minimum server version: 5.22
+	GetFileInfos(page, perPage int, opt *model.GetFileInfosOptions) ([]*model.FileInfo, *model.AppError)
+
 	// GetFile gets content of a file by it's ID
 	//
 	// @tag File