Move shared code to testlib

Signed-off-by: Andrey Berezin <a.berezin@yadro.com>

src/frostfs_testlib/shell/interfaces.py

@@ -60,6 +60,23 @@ class CommandOptions:
             self.timeout = Options.get_default_shell_timeout()
 
 
+@dataclass
+class SshCredentials:
+    """Represents ssh credentials.
+
+    Attributes:
+        ssh_login: ssh login.
+        ssh_password: ssh password as plain text (unsecure, for local setup only).
+        ssh_key_path: path to a ssh key file.
+        ssh_key_passphrase: passphrase to ssh key file.
+    """
+
+    ssh_login: str
+    ssh_password: Optional[str] = None
+    ssh_key_path: Optional[str] = None
+    ssh_key_passphrase: Optional[str] = None
+
+
 @dataclass
 class CommandResult:
     """Represents a result of a command executed via shell.

src/frostfs_testlib/shell/ssh_shell.py

@@ -29,7 +29,7 @@ reporter = get_reporter()
 class HostIsNotAvailable(Exception):
     """Raised when host is not reachable via SSH connection."""
 
-    def __init__(self, host: str = None):
+    def __init__(self, host: Optional[str] = None):
         msg = f"Host {host} is not available"
         super().__init__(msg)