[BUG][spring] -Dapis requires title-cased tags, even when tags are lowercase

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

This may be related only to Spring generator.

If a user has a tag defined as devices, the user will have to request -Dapis=Devices (or <apis>Devices</apis> in Maven). This isn't intuitive.

This was found by a user in Slack. I repro'd with:

<configuration>
    <inputSpec>lukas.yml</inputSpec>
    <generatorName>spring</generatorName>
    <configOptions>
        <sourceFolder>/</sourceFolder>
        <modelPackage>org.openapi.tools.model</modelPackage>
        <apiPackage>org.openapi.tools.api</apiPackage>
        <interfaceOnly>true</interfaceOnly>
        <java8>true</java8>
        <dateLibrary>java8</dateLibrary>
        <booleanGetterPrefix>is</booleanGetterPrefix>
        <useTags>true</useTags>
    </configOptions>
    <environmentVariables>
        <apis>Devices</apis>
    </environmentVariables>
</configuration>

openapi-generator version

4.3.0-SNAPSHOT (as of today) and below

OpenAPI declaration file content or url

openapi: 3.0.2
info:
  title: "Java template service"
  description: "Example of java microservice API defined with OpenApi v3"
  version: 1.0.0
tags:
  - name: devices
    description: Box devices
paths:
  '/api/devices':
    get:
      tags:
        - devices
      operationId: "getDevices"
      summary: List of devcies
      description: Devices
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/Device"

components:
  schemas:
    Device:
      required:
        - "id"
        - "mac"
      type: object
      properties:
        id:
          type: string
          format: uuid
          readOnly: true
          example: "EF41860F-68AD-4ABE-8D6F-3734EDDE3017"
        mac:
          type: string
          format: mac_address
          readOnly: true
          example: "112233445566"
        online:
          type: boolean
          readOnly: true
          default: false
          example: false
        

Command line used for generation

Steps to reproduce

Copied above maven config into maven example java-client.xml and ran.

Related issues/PRs

Suggest a fix

Support both title and lower cases.

Start with the Maven example configuration in java-client.xml and reproduce the Spring generator run using the provided OpenAPI document and apis setting. Trace how the Spring generator matches the lowercase devices tag, then verify that both lowercase and title-cased values select the same API output.