Listing app service certificates fails

I have the following code that tries to list existing app service certificates (3rd party) via the REST API:

`Optional existingAppCert = azure.appServices().certificates().list().stream().filter(c -> c.thumbprint().equalsIgnoreCase(MY_THUMBPRINT)).findFirst();`

This code errors out because the REST API as documented here https://docs.microsoft.com/en-us/rest/api/appservice/certificates/list returns a plain list of certificates, while the list() call is expecting a PagedList<>.

As is, this API is not usable for me via the Java SDK :(

The exception is as follows:

> Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `com.microsoft.azure.management.appservice.implementation.PageImpl` out of START_ARRAY token
at [Source: (String)"[]"; line: 1, column: 1]
at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1342)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1138)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1092)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromArray(BeanDeserializerBase.java:1454)
at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:185)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:161)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3030)
at com.microsoft.rest.serializer.JacksonAdapter.deserialize(JacksonAdapter.java:131)
at com.microsoft.rest.ServiceResponseBuilder.buildBody(ServiceResponseBuilder.java:216)
at com.microsoft.rest.ServiceResponseBuilder.build(ServiceResponseBuilder.java:110)
at com.microsoft.azure.AzureResponseBuilder.build(AzureResponseBuilder.java:56)
at com.microsoft.azure.management.appservice.implementation.CertificatesInner.listDelegate(CertificatesInner.java:213)
at com.microsoft.azure.management.appservice.implementation.CertificatesInner.access$000(CertificatesInner.java:48)
at com.microsoft.azure.management.appservice.implementation.CertificatesInner$5.call(CertificatesInner.java:200)
at com.microsoft.azure.management.appservice.implementation.CertificatesInner$5.call(CertificatesInner.java:196)
at rx.internal.operators.OnSubscribeMap$MapSubscriber.onNext(OnSubscribeMap.java:69)
at retrofit2.adapter.rxjava.CallArbiter.deliverResponse(CallArbiter.java:120)
at retrofit2.adapter.rxjava.CallArbiter.emitResponse(CallArbiter.java:102)
at retrofit2.adapter.rxjava.CallExecuteOnSubscribe.call(CallExecuteOnSubscribe.java:46)
at retrofit2.adapter.rxjava.CallExecuteOnSubscribe.call(CallExecuteOnSubscribe.java:24)
at rx.Observable.unsafeSubscribe(Observable.java:10327)
at rx.internal.operators.OnSubscribeMap.call(OnSubscribeMap.java:48)
at rx.internal.operators.OnSubscribeMap.call(OnSubscribeMap.java:33)
at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)
at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)
at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
at rx.Observable.subscribe(Observable.java:10423)
at rx.Observable.subscribe(Observable.java:10390)
at rx.observables.BlockingObservable.blockForSingle(BlockingObservable.java:443)
... 7 more

CertificatesInner.java、特に listDelegate から開始し、その想定レスポンスタイプを issue に記載されている REST API のレスポンスと比較します。空の証明書リストで失敗を再現し、証明書の一覧取得でプレーンな配列をデシリアライズでき、thumbprint によるフィルタリングをサポートできることを確認します。

索引モデルが issue の本文から書いたものです。