Update mattermost library (#2152)

* Update mattermost library

* Fix linting

vendor/github.com/hashicorp/go-hclog/nulllogger.go

@@ -0,0 +1,63 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MIT
+
+package hclog
+
+import (
+	"io"
+	"io/ioutil"
+	"log"
+)
+
+// NewNullLogger instantiates a Logger for which all calls
+// will succeed without doing anything.
+// Useful for testing purposes.
+func NewNullLogger() Logger {
+	return &nullLogger{}
+}
+
+type nullLogger struct{}
+
+func (l *nullLogger) Log(level Level, msg string, args ...interface{}) {}
+
+func (l *nullLogger) Trace(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Debug(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Info(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Warn(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Error(msg string, args ...interface{}) {}
+
+func (l *nullLogger) IsTrace() bool { return false }
+
+func (l *nullLogger) IsDebug() bool { return false }
+
+func (l *nullLogger) IsInfo() bool { return false }
+
+func (l *nullLogger) IsWarn() bool { return false }
+
+func (l *nullLogger) IsError() bool { return false }
+
+func (l *nullLogger) ImpliedArgs() []interface{} { return []interface{}{} }
+
+func (l *nullLogger) With(args ...interface{}) Logger { return l }
+
+func (l *nullLogger) Name() string { return "" }
+
+func (l *nullLogger) Named(name string) Logger { return l }
+
+func (l *nullLogger) ResetNamed(name string) Logger { return l }
+
+func (l *nullLogger) SetLevel(level Level) {}
+
+func (l *nullLogger) GetLevel() Level { return NoLevel }
+
+func (l *nullLogger) StandardLogger(opts *StandardLoggerOptions) *log.Logger {
+	return log.New(l.StandardWriter(opts), "", log.LstdFlags)
+}
+
+func (l *nullLogger) StandardWriter(opts *StandardLoggerOptions) io.Writer {
+	return ioutil.Discard
+}