[PLT-7793] Add /users/tokens/search endpoint (#8088)

* Add /users/tokens/search endpoint + tests

* Fix check-style

* Unnecessary deletion

model/user_access_token_search.go

@@ -0,0 +1,35 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+import (
+	"encoding/json"
+	"io"
+)
+
+type UserAccessTokenSearch struct {
+	Term string `json:"term"`
+}
+
+// ToJson convert a UserAccessTokenSearch to json string
+func (c *UserAccessTokenSearch) ToJson() string {
+	b, err := json.Marshal(c)
+	if err != nil {
+		return ""
+	}
+
+	return string(b)
+}
+
+// UserAccessTokenSearchJson decodes the input and returns a UserAccessTokenSearch
+func UserAccessTokenSearchFromJson(data io.Reader) *UserAccessTokenSearch {
+	decoder := json.NewDecoder(data)
+	var cs UserAccessTokenSearch
+	err := decoder.Decode(&cs)
+	if err == nil {
+		return &cs
+	}
+
+	return nil
+}