Implement basic version of local shell

Also added two simple reporters that can be used by the shell to report command execution details.

Signed-off-by: Vladimir Domnich <v.domnich@yadro.com>

shell/interfaces.py

@@ -0,0 +1,59 @@
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Optional
+
+
+@dataclass
+class InteractiveInput:
+    """
+    Interactive input for a shell command.
+
+    :attr str prompt_pattern: regular expression that defines expected prompt from the command.
+    :attr str input: user input that should be supplied to the command in response to the prompt.
+    """
+    prompt_pattern: str
+    input: str
+
+
+@dataclass
+class CommandOptions:
+    """
+    Options that control command execution.
+
+    :attr list interactive_inputs: user inputs that should be interactively supplied to
+          the command during its' execution.
+    :attr int timeout: timeout for command execution (in seconds).
+    :attr bool check: controls whether to check return code of the command. Set to False to
+          ignore non-zero return codes.
+    """
+    interactive_inputs: Optional[list[InteractiveInput]] = None
+    timeout: int = 30
+    check: bool = True
+
+
+@dataclass
+class CommandResult:
+    """
+    Represents a result of a command executed via shell.
+    """
+    stdout: str
+    stderr: str
+    return_code: int
+
+
+class Shell(ABC):
+    """
+    Interface of a command shell on some system (local or remote).
+    """
+
+    @abstractmethod
+    def exec(self, command: str, options: Optional[CommandOptions] = None) -> CommandResult:
+        """
+        Executes specified command on this shell. To execute interactive command, user inputs
+        should be specified in *options*.
+
+        :param str command: command to execute on the shell.
+        :param CommandOptions options: options that control command execution.
+        :return command result.
+        """
+        pass