Adding of index on array elements is unnecessary

[Mazgis47]

Currently, the index of each array item is appended in a form of [x] e.g. [0]. However swagger does not append that and I believe such indexes should not be added by oapi-codegen too.

Example:

openapi: 3.0.3
info:
 version: 0.0.1
 title: Test array
 description: Test Array
servers:
 - url: http://localhost:8081
 description: local
tags:
 - name: test
paths:
 /v1/asns:
 get:
 summary: Search Asn
 operationId: searchAsn
 tags:
 - asn
 parameters:
 - $ref: "#/components/parameters/QueryTenantUUID"
 responses:
 "200":
 description: Success
 content:
 application/json:
 schema:
 $ref: "#/components/schemas/AsnsResponse"
components:
 parameters:
 QueryTenantUUID:
 name: tenant_uuid
 in: query
 style: deepObject
 schema:
 $ref: "#/components/schemas/Filter"
 examples:
 advanced:
 value:
 op: eq
 vals:
 - aaaaaa
 - bbbbbb
 schemas:
 Filter:
 type: object
 required:
 - op
 - vals
 properties:
 op:
 description: Filter operation like equals, greater than, not equals, less than ...
 type: string
 enum:
 - eq
 - ne
 - lt
 - lte
 - gt
 - gte
 - like
 vals:
 type: array
 items: {}
 description: Values can be any type for filtering
 AsnsResponse:
 type: object
 properties:
 data:
 type: array
 items:
 $ref: "#/components/schemas/Asn"
 Asn:
 type: object
 properties:
 tenant_uuid:
 type: string
 format: uuid
 example: "aaaaaa"

https://editor.swagger.io/ generates the request without indexes, and this difference causes problems to parse the parameters correctly.

http://localhost/v1/asns?tenant_uuid%5Bop%5D=eq&tenant_uuid%5Bvals%5D=aaaaaa&tenant_uuid%5Bvals%5D=bbbbbb
without encoding:
http://localhost/v1/asns?tenant_uuid[op]=eq&tenant_uuid[vals]=aaaaaa&tenant_uuid[vals]=bbbbbb

codegen generates with the indexes as:
http://localhost/v1/asns?tenant_uuid[op]=eq&tenant_uuid[vals][0]=aaaaaa&tenant_uuid[vals][1]=bbbbbb

[mromaszewicz]

There are two competing conventions here, because OpenAPI 3.0 explicitly left this as undefined behavior, and we picked the indexed approach since it's more obvious.

1. Repeated keys (no index): filter[vals]=a&filter[vals]=b — used by Swagger UI, Rails-style (also uses filter[vals][]=a)
2. Indexed keys: filter[vals][0]=a&filter[vals][1]=b — used by Node.js qs library, current oapi-codegen

What I'm going to do is support parsing both formats in binding and unmarshaling, however, I can't change the way this is marshaled because we will break existing users. We'll be flexible at accepting both.