assisted-service panics if pull secret contains null

When the user's pull secret contains a JSON null in the "auth" or "email" keys, assisted service crashes when we attempt to create the cluster:

May 31 21:06:27 example.dev.local service[3389]: time="2023-05-31T09:06:27Z" level=error msg="Failed to registered cluster example with id 3648b06e-4745-4542-9421-78ae2e249c0d" func="github.
com/openshift/assisted-service/internal/bminventory.(*bareMetalInventory).RegisterClusterInternal.func1" file="/src/internal/bminventory/inventory.go:448" cluster_id=3648b06e-4745-4542-9421-
78ae2e249c0d go-id=162 pkg=Inventory request_id=1252f666-cf5c-4aae-9be7-7b7a579b5bf6
May 31 21:06:27 example.dev.local service[3389]: 2023/05/31 09:06:27 http: panic serving 10.116.24.118:46262: interface conversion: interface {} is nil, not string
May 31 21:06:27 example.dev.local service[3389]: goroutine 162 [running]:
May 31 21:06:27 example.dev.local service[3389]: net/http.(*conn).serve.func1()
May 31 21:06:27 example.dev.local service[3389]:         /usr/lib/golang/src/net/http/server.go:1850 +0xbf
May 31 21:06:27 example.dev.local service[3389]: panic({0x25d0000, 0xc00148d7d0})
May 31 21:06:27 example.dev.local service[3389]:         /usr/lib/golang/src/runtime/panic.go:890 +0x262
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/internal/cluster/validations.ParsePullSecret({0xc001ed0780, 0x1c6})
May 31 21:06:27 example.dev.local service[3389]:         /src/internal/cluster/validations/validations.go:106 +0x718
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/internal/cluster/validations.(*registryPullSecretValidator).ValidatePullSecret(0xc0005880c0, {0xc001ed0780?, 0x7?}, {0x29916da, 0x5})
May 31 21:06:27 example.dev.local service[3389]:         /src/internal/cluster/validations/validations.go:160 +0x54
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/internal/bminventory.(*bareMetalInventory).ValidatePullSecret(...)
May 31 21:06:27 example.dev.local service[3389]:         /src/internal/bminventory/inventory.go:279
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/internal/bminventory.(*bareMetalInventory).RegisterClusterInternal(0xc00112f880, {0x2fd3e20, 0xc00148cd50}, 0x0, {0xc0007c0400, 0xc0008d69a0})
May 31 21:06:27 example.dev.local service[3389]:         /src/internal/bminventory/inventory.go:564 +0x16d0
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/internal/bminventory.(*bareMetalInventory).V2RegisterCluster(0x2fd3e20?, {0x2fd3e20?, 0xc00148cd50?}, {0xc0007c0400?, 0xc0008d69a0?})
May 31 21:06:27 example.dev.local service[3389]:         /src/internal/bminventory/inventory_v2_handlers.go:42 +0x39
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/restapi.HandlerAPI.func59({0xc0007c0400?, 0xc0008d69a0?}, {0x2390b20?, 0xc0014e0240?})
May 31 21:06:27 example.dev.local service[3389]:         /src/restapi/configure_assisted_install.go:639 +0xaf
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/restapi/operations/installer.V2RegisterClusterHandlerFunc.Handle(0xc000a9d068?, {0xc0007c0400?, 0xc0008d69a0?}, {0x2390b20?, 0xc0014e0240?})
May 31 21:06:27 example.dev.local service[3389]:         /src/restapi/operations/installer/v2_register_cluster.go:19 +0x3d
May 31 21:06:27 example.dev.local service[3389]: github.com/openshift/assisted-service/restapi/operations/installer.(*V2RegisterCluster).ServeHTTP(0xc000571470, {0x2fc7140, 0xc00034c040}, 0xc0007c0400)
May 31 21:06:27 example.dev.local service[3389]:         /src/restapi/operations/installer/v2_register_cluster.go:66 +0x298
May 31 21:06:27 example.dev.local service[3389]: github.com/go-openapi/runtime/middleware.NewOperationExecutor.func1({0x2fc7140, 0xc00034c040}, 0xc0007c0400)
May 31 21:06:27 example.dev.local service[3389]:         /src/vendor/github.com/go-openapi/runtime/middleware/operation.go:28 +0x59

4.12.17

Probably 100%

1. Add to the pull secret in install-config.yaml an auth like:

        "example.com": {
          "auth": null,
          "email": null
        }

2. Generate the agent ISO as usual using "openshift-install agent create image"
3. Boot the ISO on the cluster hosts.

The create-cluster-and-infraenv.service fails to complete. In its log it reports:

    Failed to register cluster with assisted-service: Post \"http://10.1.1.2:8090/api/assisted-install/v2/clusters\": EOF

Cluster is installed.

This is particularly difficult to debug because users don't generally give us their pull secrets. The pull secret file in the agent-gather bundle has individual fields redacted, so it is a better guide than the install-config where the whole thing may be redacted.