Add some basic provider config code

server/intake/__init__.py

@@ -0,0 +1 @@
+from .provider import Config, Setting

server/intake/provider.py

@@ -0,0 +1,39 @@
+class SettingMissingError(Exception):
+    """
+    No value was provided for a required setting.
+    """
+    def __init__(self, missing_names):
+        super().__init__("Missing required settings: {}".format(", ".join(missing_names)))
+        self.missing_names = missing_names
+
+
+class Setting:
+    """
+    A setting value declared by a provider and defined by a source.
+    """
+
+    def __init__(self, required=False, default=None):
+        self.required = required
+        self.value = default
+
+
+class Config:
+    """
+    Base class for provider configs.
+    """
+
+    name = Setting(required=True)
+
+    provider = Setting(required=True)
+
+    def __init__(self, **kwargs):
+        setting_names = [name for name in dir(self) if not name.startswith("__")]
+        missing = []
+        for setting_name in setting_names:
+            setting: Setting = getattr(self, setting_name)
+            if setting_name in kwargs:
+                setting.value = kwargs[setting_name]
+            elif setting.required:
+                missing.append(setting_name)
+        if missing:
+            raise SettingMissingError(missing)