Unable to login with username identifier if username has upper case letters

[NickUfer]

Describe the bug

Users are unable to login with an identifier which is not an email and which has upper case letters at registration. They would have to enter their identifier in lowercase letters to login.

Reproducing the bug

• Define another identifier which is not an email. For this example use "username"
• Create an account with a username with upper case letters, for example "TestAccount"
• Try to login with "TestAccount" as the identifier. This will not work, but "testaccount" will

Identity Schema:

{
  "$id": "https://schemas.ory.sh/presets/kratos/quickstart/email-password/identity.schema.json",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Person",
  "type": "object",
  "properties": {
    "traits": {
      "type": "object",
      "properties": {
        "email": {
          "type": "string",
          "format": "email",
          "title": "E-Mail",
          "minLength": 3,
          "ory.sh/kratos": {
            "credentials": {
              "password": {
                "identifier": true
              }
            },
            "verification": {
              "via": "email"
            },
            "recovery": {
              "via": "email"
            }
          }
        },
        "username": {
          "type": "string",
          "title": "Username",
          "minLength": 3,
          "ory.sh/kratos": {
            "credentials": {
              "password": {
                "identifier": true
              }
            }
          }
        }
      },
      "required": [
        "email",
        "username"
      ],
      "additionalProperties": false
    }
  }
}

Expected behavior

Users should be able to login with all their identifiers regardless of case.

Environment

• Version: ddcffff
• Environment: Ubuntu, Docker