Add ability to specify separator used in proxy headers (#18336)

frigate/config/proxy.py

@@ -1,6 +1,6 @@
 from typing import Optional
 
-from pydantic import Field
+from pydantic import Field, field_validator
 
 from .base import FrigateBaseModel
 from .env import EnvString
@@ -33,3 +33,14 @@ class ProxyConfig(FrigateBaseModel):
     default_role: Optional[str] = Field(
         default="viewer", title="Default role for proxy users."
     )
+    separator: Optional[str] = Field(
+        default=",",
+        title="The character used to separate values in a mapped header.",
+    )
+
+    @field_validator("separator", mode="before")
+    @classmethod
+    def validate_separator_length(cls, v):
+        if v is not None and len(v) != 1:
+            raise ValueError("Separator must be exactly one character")
+        return v