Endpoint generation from OpenAPI fails for fields with examples

[nikolaiser]

Describe the bug
EndpointGen.fromOpenAPI fails if one of the components contains a field with an example

To Reproduce

The following scala-cli script

//> using scala 2.13.12
//> using repository sonatype:snapshots
//> using dep dev.zio::zio-http-gen:3.0.0-RC4+41-2d267b56-SNAPSHOT
//> using dep dev.zio::zio-json-yaml:0.6.2

import zio.http.gen.openapi.EndpointGen
import zio.http.endpoint.openapi.OpenAPI
import zio.http.endpoint.openapi.JsonSchema
import zio.json.yaml._
import zio.schema.codec.JsonCodec

object Main {

  val openapiYaml = """
                      |openapi: 3.0.3
                      |info:
                      | title: Example
                      | description: Example API documentation
                      | version: 1.0.0
                      |paths:
                      | /foo:
                      |   post:
                      |     requestBody:
                      |       content:
                      |         application/json:
                      |           schema:
                      |             $ref: '#/components/schemas/Bar' 
                      |     responses:
                      |       '200':
                      |         description: Success
                      |
                      |components:
                      | schemas:
                      |   Bar:
                      |     type: object
                      |     properties:
                      |       stringField:
                      |         type: string
                      |         example: 'abc'
  """.stripMargin

  implicit val openapiDecoder = JsonCodec.jsonDecoder(OpenAPI.schema)

  def main(args: Array[String]) = {
    val openapi = openapiYaml.fromYaml[OpenAPI].toOption.get
    println(EndpointGen.fromOpenAPI(openapi))
  }
}

Throws the exception

Exception in thread "main" java.lang.Exception: Could not generate code for field stringField of object stringField
        at zio.http.gen.openapi.EndpointGen$$anonfun$6.$anonfun$applyOrElse$11(EndpointGen.scala:654)
        at scala.Option.getOrElse(Option.scala:201)
        at zio.http.gen.openapi.EndpointGen$$anonfun$6.applyOrElse(EndpointGen.scala:654)
        at zio.http.gen.openapi.EndpointGen$$anonfun$6.applyOrElse(EndpointGen.scala:650)
        at scala.collection.StrictOptimizedIterableOps.collect(StrictOptimizedIterableOps.scala:151)
        at scala.collection.StrictOptimizedIterableOps.collect$(StrictOptimizedIterableOps.scala:136)
        at scala.collection.immutable.Map$Map1.collect(Map.scala:259)
        at zio.http.gen.openapi.EndpointGen.schemaToCode(EndpointGen.scala:650)
        at zio.http.gen.openapi.EndpointGen.$anonfun$fromOpenAPI$16(EndpointGen.scala:119)
        at scala.collection.StrictOptimizedIterableOps.flatMap(StrictOptimizedIterableOps.scala:118)
        at scala.collection.StrictOptimizedIterableOps.flatMap$(StrictOptimizedIterableOps.scala:105)
        at scala.collection.immutable.Map$Map1.flatMap(Map.scala:259)
        at zio.http.gen.openapi.EndpointGen.$anonfun$fromOpenAPI$15(EndpointGen.scala:108)
        at scala.collection.immutable.List.flatMap(List.scala:293)
        at zio.http.gen.openapi.EndpointGen.fromOpenAPI(EndpointGen.scala:107)
        at zio.http.gen.openapi.EndpointGen$.fromOpenAPI(EndpointGen.scala:32)
        at Main$.main(example-fail.scala:46)
        at Main.main(example-fail.scala)

Expected behaviour
EndpointGen.fromOpenAPI can correctly generate code for schemas with examples

[jdegoes]

/bounty $50

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Attempt	Started (GMT+2)	Solution
🟢 @987Nabil		#2643

[algora-pbc]

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