Storage clients add new builder: NewWithEndpoint() to allow build client with a custom endpoint

[magodo]

New builder: NewWithEndpoint() to allow build client with a custom endpoint.

Refer to hashicorp/go-azure-sdk#568 for the motivation of this PR.

Test

💤  ACCTEST=1 ARM_ENVIRONMENT=public go test -timeout 60m ./...
?       github.com/tombuildsstuff/giovanni/example/azuread-auth [no test files]
?       github.com/tombuildsstuff/giovanni/example/file-auth    [no test files]
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/blob/accounts     128.955s
?       github.com/tombuildsstuff/giovanni/storage/internal/endpoints   [no test files]
?       github.com/tombuildsstuff/giovanni/storage/internal/testhelpers [no test files]
?       github.com/tombuildsstuff/giovanni/version      [no test files]
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/blob/blobs        1252.747s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/blob/containers   65.316s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/datalakestore/filesystems 122.076s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/datalakestore/paths       191.379s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/file/directories  65.488s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/file/files        1159.572s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/file/shares       309.245s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/queue/messages    129.599s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/queue/queues      124.485s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/table/entities    127.484s
ok      github.com/tombuildsstuff/giovanni/storage/2020-08-04/table/tables      125.937s
ok      github.com/tombuildsstuff/giovanni/storage/accesscontrol        0.004s
ok      github.com/tombuildsstuff/giovanni/storage/internal/metadata    0.003s

[magodo]

@tombuildsstuff After migrating to the go-azure-sdk data plane sdk, this PR seems to be fine to close?

[tombuildsstuff]

@magodo yeah, indeed - apologies this one didn't land before the refactor, but given this is supported when using the new base layer I'm going to suggest we close this one.

One thing we'll do before vendoring the version including the new base layer is to include a Meta Client for all of the Data Plane Clients, as we're doing in hashicorp/go-azure-sdk (tracked in #76) - which should make this easier in the provider 👍

[favoretti]

@tombuildsstuff ah, so this is still work in progress? I tried retesting hashicorp/terraform-provider-azurerm#22583 and that one kept failing since endpoints resolver in giovanni is still assuming they are static.