Add Healthcheck Route

This is a route that connects to the database, connects to ldap, and returns a json blob stating whether or not it can connect.

This should allow us to more reasonably monitor on whether or not packet is up

How I want this to work
```
GET /api/v1/healthcheck
```
That would return 200 only when both ldap and the database connect correctly, and a 5XX range response when they don't. Different 5XX code for ldap down, sql down and both down
```json
{
"ldap": true,
"database": true
}
```
Return the json no matter what the status code is.
Even better would be
```json
{
"ldap": {
"status": true,
"server": "stone.csh.rit.edu"
},
"database": {
"status": true,
"server": "mysql.csh.rit.edu"
},
}
```

首先定位 Flask 路由注册以及现有的数据库和 LDAP 连接辅助函数。添加 GET /api/v1/healthcheck，确保每种结果都返回 JSON；当 LDAP、数据库或两者都发生故障时，分别返回不同的 5XX 响应，并验证健康状态响应会报告这两个依赖项。

由索引模型根据 Issue 内容生成。