fix(anta.tests): Cleaning up BFD tests module (#926)

* Refactor: VerifyBFDPeersRegProtocols, VerifyBFDPeersIntervals, VerifyBFDSpecificPeers

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Updated unit tests and docs

* Addressed review commentsL: updated failure msgs

* updated failure msgs: removed , and ;

* updated docstring

---------

Co-authored-by: VitthalMagadum <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Guillaume Mulocher <[email protected]>

anta/input_models/bfd.py

@@ -0,0 +1,37 @@
+# Copyright (c) 2023-2024 Arista Networks, Inc.
+# Use of this source code is governed by the Apache License 2.0
+# that can be found in the LICENSE file.
+"""Module containing input models for BFD tests."""
+
+from __future__ import annotations
+
+from ipaddress import IPv4Address
+
+from pydantic import BaseModel, ConfigDict
+
+from anta.custom_types import BfdInterval, BfdMultiplier, BfdProtocol
+
+
+class BFDPeer(BaseModel):
+    """BFD (Bidirectional Forwarding Detection) model representing the peer details.
+
+    Only IPv4 peers are supported for now.
+    """
+
+    model_config = ConfigDict(extra="forbid")
+    peer_address: IPv4Address
+    """IPv4 address of a BFD peer."""
+    vrf: str = "default"
+    """Optional VRF for the BFD peer. Defaults to `default`."""
+    tx_interval: BfdInterval | None = None
+    """Tx interval of BFD peer in milliseconds. Required field in the `VerifyBFDPeersIntervals` test."""
+    rx_interval: BfdInterval | None = None
+    """Rx interval of BFD peer in milliseconds. Required field in the `VerifyBFDPeersIntervals` test."""
+    multiplier: BfdMultiplier | None = None
+    """Multiplier of BFD peer. Required field in the `VerifyBFDPeersIntervals` test."""
+    protocols: list[BfdProtocol] | None = None
+    """List of protocols to be verified. Required field in the `VerifyBFDPeersRegProtocols` test."""
+
+    def __str__(self) -> str:
+        """Return a human-readable string representation of the BFDPeer for reporting."""
+        return f"Peer: {self.peer_address} VRF: {self.vrf}"