Add multi-username activity support

app/settings.py

@@ -1,9 +1,21 @@
 from functools import lru_cache
 
-from pydantic import Field
+from pydantic import Field, field_validator
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
+def split_usernames(raw: str) -> list[str]:
+    usernames: list[str] = []
+    seen: set[str] = set()
+    for part in raw.split(","):
+        username = part.strip()
+        if not username or username in seen:
+            continue
+        seen.add(username)
+        usernames.append(username)
+    return usernames
+
+
 class Settings(BaseSettings):
     model_config = SettingsConfigDict(env_file=".env", case_sensitive=False)
 
@@ -20,6 +32,21 @@ class Settings(BaseSettings):
     default_theme: str = Field(default="light", alias="DEFAULT_THEME")
     service_title: str = Field(default="git-activity-merge", alias="SERVICE_TITLE")
 
+    @field_validator("github_username", "gitea_username")
+    @classmethod
+    def _validate_username_list(cls, value: str) -> str:
+        if not split_usernames(value):
+            raise ValueError("must contain at least one username")
+        return value
+
+    @property
+    def github_usernames(self) -> list[str]:
+        return split_usernames(self.github_username)
+
+    @property
+    def gitea_usernames(self) -> list[str]:
+        return split_usernames(self.gitea_username)
+
 
 @lru_cache(maxsize=1)
 def get_settings() -> Settings: