feat(nodestore): File-based nodestore backend (#41967)

Output of a recent lightning talk. This is a `nodestore` backend that
saves nodes as plaintext files in a folder. Very useful for debugging,
testing edge cases, etc.

src/sentry/nodestore/filesystem/__init__.py

@@ -0,0 +1 @@
+from .backend import FileSystemNodeStorage  # NOQA

src/sentry/nodestore/filesystem/backend.py

@@ -0,0 +1,54 @@
+import datetime
+import os
+
+from django.conf import settings
+from django.utils import timezone
+
+from sentry.nodestore.base import NodeStorage
+
+
+class FileSystemNodeStorage(NodeStorage):
+    """
+    A simple backend that saves each node as a file. Only appropriate for
+    debugging and development!
+    """
+
+    def __init__(self, path=None):
+        self.path: str = ""
+
+        if not settings.DEBUG:
+            raise ValueError("FileSystemNodeStorage should only be used in development!")
+        if path:
+            self.path = os.path.abspath(os.path.expanduser(path))
+        else:
+            self.path = os.path.abspath(os.path.join(os.path.dirname(__file__), "./nodes"))
+
+    def _get_bytes(self, id: str):
+        with open(self.node_path(id), "rb") as file:
+            return file.read()
+
+    def _set_bytes(self, id: str, data: bytes, ttl=0):
+        with open(self.node_path(id), "wb") as file:
+            file.write(data)
+
+    def delete(self, id):
+        os.remove(self.node_path(id))
+
+    def cleanup(self, cutoff: datetime.datetime):
+        for filename in os.listdir(self.path):
+            path = os.path.join(self.path, filename)
+            creation_datetime = datetime.datetime.fromtimestamp(os.path.getctime(path)).replace(
+                tzinfo=timezone.utc
+            )
+
+            if creation_datetime > cutoff:
+                os.remove(path)
+
+    def bootstrap(self):
+        try:
+            os.mkdir(self.path)
+        except FileExistsError:
+            pass
+
+    def node_path(self, id: str):
+        return os.path.join(self.path, f"{id}.json")