tell it where the stripe key can be found

morph/grid.config.json

 { "publicStoragePort": 8898
 , "ristrettoSigningKeyPath": "../../PrivateStorageSecrets/ristretto.signing-key"
+, "stripeSecretKeyPath": "../../PrivateStorageSecrets/stripe.secret"
 , "issuerDomain": "payments.privatestorage.io"
 , "letsEncryptAdminEmail": "jean-paul@privatestorage.io"
 }

morph/testing-grid.config.json

 { "publicStoragePort": 8898
 , "ristrettoSigningKeyPath": "../../PrivateStorageSecrets/ristretto.signing-key"
+, "stripeSecretKeyPath": "../../PrivateStorageSecrets/stripe.secret"
 , "issuerDomain": "payments.privatestorage-staging.com"
 , "letsEncryptAdminEmail": "jean-paul@privatestorage.io"
 }