docs(credentials): Update website domain docs (#2287)

website/content/docs/concepts/domain-model/credential-stores.mdx

@@ -60,7 +60,7 @@ A Vault credential store has the following additional attributes:
 
 ### Static Credential Store Attributes
 
-A Static credential store has no additional attributes and only supports the optional attributes.
+A static credential store has no type-specific attributes.
 
 ## Referenced By
 

website/content/docs/concepts/domain-model/credentials.mdx

@@ -13,15 +13,26 @@ on a [host][] for a [session][].
 
 ## Attributes
 
-## Credential types
+## Credential Types
 
 Optionally, credentials can be typed to indicate compliance with a specific
-format. For example, Boundary allows for `username_password` credentials that
-contain the following fields:
+format.
 
-- `username` - The username field assocaited with the credential.
+### Username Password
 
-- `password` - The password field assocaited with the credential.
+`username_password` credentials contain the following fields:
+
+- `username` - The username field associated with the credential.
+
+- `password` - The password field associated with the credential.
+
+### SSH Private Key
+
+`ssh_private_key` credentials contain the following fields:
+
+- `username` - The username field associated with the credential.
+
+- `private_key` - The private key field associated with the credential.
 
 ## Referenced By