[redbot.setup] Ask for confirmation when passed instance name contains hyphens + allow to use dots (#3920)

* Change regex and the error message

* few changes see ^^^ GH comment

if it doesn't pass the RegEx `[a-zA-Z0-9_\.]*` then:
- if on Linux and contains a "-" anywhere, not allowed
- if it contains a space or starts with a "-", not allowed
- if the top two don't trigger, then `confirm()` with the user.

* black why

* 3.3.9

* fk

* ty aika

* review :aha:

* oopsie

Co-authored-by: jack1142 <6032823+jack1142@users.noreply.github.com>

* this is just vexed tries and jack fixes

Co-authored-by: jack1142 <6032823+jack1142@users.noreply.github.com>

* quite sad really

Co-authored-by: jack1142 <6032823+jack1142@users.noreply.github.com>

Co-authored-by: jack1142 <6032823+jack1142@users.noreply.github.com>

redbot/setup.py

@@ -12,6 +12,7 @@ from typing import Dict, Any, Optional, Union
 import appdirs
 import click
 
+from redbot.core.cli import confirm
 from redbot.core.utils._internal_utils import safe_delete, create_backup as red_create_backup
 from redbot.core import config, data_manager, drivers
 from redbot.core.drivers import BackendType, IdentifierData
@@ -128,16 +129,23 @@ def get_name() -> str:
         print(
             "Please enter a name for your instance,"
             " it will be used to run your bot from here on out.\n"
-            "This name is case-sensitive and can only include characters"
-            " A-z, numbers, underscores, and hyphens."
+            "This name is case-sensitive and should only include characters"
+            " A-z, numbers, underscores (_) and periods (.)."
         )
         name = input("> ")
-        if re.fullmatch(r"[a-zA-Z0-9_\-]*", name) is None:
+        if re.fullmatch(r"[A-Za-z0-9_\.\-]*", name) is None:
             print(
-                "ERROR: Instance name can only include"
-                " characters A-z, numbers, underscores, and hyphens!"
+                "ERROR: Instance names can only include characters A-z, numbers, "
+                "underscores (_) and periods (.)."
             )
             name = ""
+        elif "-" in name and not confirm(
+            "Hyphens (-) in instance names may cause issues. Are you sure you want to continue with this instance name?",
+            default=False,
+        ):
+            name = ""
+
+        print()  # new line for aesthetics
     return name