POST in openapi - api

Question

I'm new in the world of API. I want to do an API using swagger in yaml. My teacher given us a snippet of code that should simulate a login API, but Bearer style. I want to map the generated identifier with the correlated name
paths:
/session:
post:
tags: ["login"]
summary: Logs in the user
description: |-
If the user does not exist, it will be created,
and an identifier is returned.
If the user exists, the user identifier is returned.
operationId: doLogin
requestBody:
description: User details
content:
application/json:
schema:
type: object
properties:
name:
type: string
example: Jason
pattern: 'ˆ.*?$'
minLength: 3
maxLength: 16
required: true
responses:
'201':
description: User log-in action successfully
content:
application/json:
schema:
type: object
properties:
identifier:
# change here if you decide to use an integer
# or any other type of identifier
type: string
example: "abcdef012345"
/session/{identifier}:
get:
summary: Get username
description: Get username from identifier
operationId: getUsername
parameters:
- name: identifier
in: path
description: User ID
required: true
schema:
$ref: "#/components/schemas/User/properties/identifier"
responses:
'200':
description: 'User exists'
content:
application/json:
schema:
$ref: "#/components/schemas/User"
components:
schemas:
User:
type: object
properties:
identifier:
type: string
example: "abcdef012345"
name:
type: string
example: "Jason"
I tried adding the "/session/{identifier}" path, but the get never retrieve the correct information. How can I do it?
Thank you in advance