Storing user-agent?

Question

Database

When a user is authorized, his user-agent is written to the database.
On average, a title is usually less than 200 characters, so varchar(200) is more than enough for it.
Suppose an attacker tries to break the system and sends a user-agent 1000 characters long.
The application handles this by simply storing the first 200 characters from the title.
Is this the right approach?
Where in such cases it is correct to store limits? Those. to set the sizes of the data in a DB in constants? in configs? Leave magic numbers?
I used such an approach that in the migrations for the database, the constants specified in the code were used, and the validators were attached to the same constants. How correct is this?
Almost pseudocode

migration.php

use Constants;

class Migration {
    public function run() {
        $this->db->addColumn('table', 'column', Constants::USER_AGENT_LENGTH);
    }
}


Controller.php

use Constants;

class Controller {
    public function login(Request $request) {
         $userAgent = substr($request->header('user-agent'), 0, Constants::USER_AGENT_LENGTH);
    }
}

Answer 1

it’s not clear why UA
store the fingerprint then, in general, you don’t need to bathe