POST| /signin

## Route: POST api/v1/signin/employee
## Route: POST api/v1/signin/company

### Acceptance Criteria
- [ ] Validation
- [ ] DB query
- [ ] Response
----------------------------------------------

### Validation
```js
{
email: joi.string().email().required(),
password: joi.string().alphanum().min(6).required()
}
```
### DB query
```sql
select (id, password, first_name, last_name) from user where email = $1
select (id, password, name) from company where email = $1
```
### Response
**Success**
- company
```js
{
statusCode:200,
data : [{
id: 1,
name: 'full name',
password: 'password',
}]
}‏
```

- user
```js
{
statusCode:200,
data : [{
id: 1,
first_name: 'first',
last_name: 'last',
password: 'password',
}]
}‏
```

**Failed**
- email not exists
```js
{
statusCode:409,
message:"Email is not found!"
}
```
- password wrong
```js
{
statusCode:409,
message:"Password is wrong"
}
```

- validation error
```js
{
statusCode:400,
message : "Bad request"
}
```

Start by locating the existing API route and entry points for POST api/v1/signin/employee and POST api/v1/signin/company, then review nearby validation and database-query patterns. Done means both routes handle the listed validation, queries, success response, and failure status messages.

Written by the indexing model from the issue text.