refactor: Restructure project layout and clean up dependencies (#30)

This commit introduces a significant reorganization of the project structure to improve maintainability and clarity.

Key changes include:
- Adjusted the directory layout for a more logical module organization.
- Removed unused crate dependencies, reducing the overall project size and potentially speeding up build times.
- Updated import paths and configuration files to reflect the structural changes.

crates/madmin/src/group.rs

@@ -0,0 +1,45 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use serde::Deserialize;
+use serde::Serialize;
+use time::OffsetDateTime;
+
+#[derive(Debug, Serialize, Deserialize, Default)]
+#[serde(rename_all = "lowercase")]
+pub enum GroupStatus {
+    #[default]
+    Enabled,
+    Disabled,
+}
+
+#[derive(Debug, Serialize, Deserialize, Default)]
+pub struct GroupAddRemove {
+    pub group: String,
+    pub members: Vec<String>,
+    #[serde(rename = "groupStatus")]
+    pub status: GroupStatus,
+    #[serde(rename = "isRemove")]
+    pub is_remove: bool,
+}
+
+#[derive(Debug, Serialize, Deserialize, Default)]
+pub struct GroupDesc {
+    pub name: String,
+    pub status: String,
+    pub members: Vec<String>,
+    pub policy: String,
+    #[serde(rename = "updatedAt", skip_serializing_if = "Option::is_none")]
+    pub updated_at: Option<OffsetDateTime>,
+}