[FEATURE] Extend subscription syntax (#790)

Extends the subscription.yaml syntax at the cost of introducing a breaking change.

# New Syntax
## Mix-n-match presets and indent variables
```
# Can mix/match presets and indent override variables.
# Uses presets TV Show, Only Recent and assigns Kids, TV-Y to subscription_indent_1 and _2
TV Show | = Kids | = TV-Y | Only Recent:
  "Jake Trains": "https://..."
```

## Subscriptions with list-value support
```
TV Show | = Kids | = TV-Y | Only Recent:
  "Jake Trains":
    - "https://url.1..."  # Assigns to subscription_value and subscription_value_1
    - "https://url.2..."  # Assigns to subscription_value_2
```

## Subscriptions with override-keys support
```
TV Show | = Kids | = TV-Y | Only Recent:
  "~Jake Trains":  # the ~ means "all keys underneath get assigned as override variables"
    url: "https://url.1..."  # Assigns to url
    url2: "https://url.2..."  # Assigns to url2
```

# Breaking Changes
In the TV show subscriptions example (https://github.com/jmbannon/ytdl-sub/blob/master/examples/tv_show_subscriptions.yaml), it had
```
TV Show Full Archive:
  # Sets "Kids" for genre, "TV-Y" for content rating
  = Kids | TV-Y:
    "Jake Trains": "https://www.youtube.com/@JakeTrains"
    "Kids Toys Play": "https://www.youtube.com/@KidsToysPlayChannel"
```
This must be changed to
```
TV Show Full Archive:
  # Sets "Kids" for genre, "TV-Y" for content rating
  = Kids | = TV-Y:  # Each indent variable assignment must have an = before it
    "Jake Trains": "https://www.youtube.com/@JakeTrains"
    "Kids Toys Play": "https://www.youtube.com/@KidsToysPlayChannel"
```

examples/tv_show_subscriptions.yaml

@@ -13,12 +13,12 @@ TV Show Full Archive:
     "Opeth": "https://www.youtube.com/channel/UCmQSJTFZaXN85gYk6W3XbdQ"
 
   # Sets "Kids" for genre, "TV-Y" for content rating
-  = Kids | TV-Y:
+  = Kids | = TV-Y:
     "Jake Trains": "https://www.youtube.com/@JakeTrains"
     "Kids Toys Play": "https://www.youtube.com/@KidsToysPlayChannel"
 
 
 # All subscriptions under this will use the `TV Show Only Recent` preset
 TV Show Only Recent:
-  = News | TV-14:
+  = News | = TV-14:
     "BBC": "https://www.youtube.com/@BBCNews"

src/ytdl_sub/config/config_validator.py

@@ -10,6 +10,7 @@
 from ytdl_sub.config.defaults import DEFAULT_LOCK_DIRECTORY
 from ytdl_sub.config.defaults import MAX_FILE_NAME_BYTES
 from ytdl_sub.prebuilt_presets import PREBUILT_PRESETS
+from ytdl_sub.subscriptions.utils import SUBSCRIPTION_VALUE_CONFIG_KEY
 from ytdl_sub.validators.file_path_validators import FFmpegFileValidator
 from ytdl_sub.validators.file_path_validators import FFprobeFileValidator
 from ytdl_sub.validators.strict_dict_validator import StrictDictValidator
@@ -106,7 +107,7 @@ class ConfigOptions(StrictDictValidator):
         "ffprobe_path",
         "file_name_max_bytes",
         "experimental",
-        "subscription_value",
+        SUBSCRIPTION_VALUE_CONFIG_KEY,
     }
 
     def __init__(self, name: str, value: Any):
@@ -142,7 +143,7 @@ def __init__(self, name: str, value: Any):
             key="file_name_max_bytes", validator=IntValidator, default=MAX_FILE_NAME_BYTES
         )
         self._subscription_value = self._validate_key_if_present(
-            key="subscription_value", validator=StringValidator
+            key=SUBSCRIPTION_VALUE_CONFIG_KEY, validator=StringValidator
         )
 
     @property

src/ytdl_sub/config/preset_options.py

@@ -9,6 +9,7 @@
 
 from ytdl_sub.config.defaults import DEFAULT_DOWNLOAD_ARCHIVE_NAME
 from ytdl_sub.entries.entry import Entry
+from ytdl_sub.subscriptions.utils import SUBSCRIPTION_NAME
 from ytdl_sub.utils.exceptions import ValidationException
 from ytdl_sub.validators.file_path_validators import OverridesStringFormatterFilePathValidator
 from ytdl_sub.validators.file_path_validators import StringFormatterFileNameValidator
@@ -120,45 +121,9 @@ class YTDLOptions(LiteralDictValidator):
     """
 
 
-class OverridesVariables(DictFormatterValidator):
-    """
-    Override variables that are automatically added to every subscription.
-    """
-
-    def _add_override_variable(self, key_name: str, format_string: str, sanitize: bool = False):
-        if sanitize:
-            key_name = f"{key_name}_sanitized"
-            format_string = sanitize_filename(format_string)
-
-        self._value[key_name] = StringFormatterValidator(
-            name="__should_never_fail__",
-            value=format_string,
-        )
-
-    def __init__(self, name, value):
-        super().__init__(name, value)
-
-        # Add sanitized and non-sanitized override variables
-        for sanitize in [True, False]:
-            self._add_override_variable(
-                key_name="subscription_name",
-                format_string=self.subscription_name,
-                sanitize=sanitize,
-            )
-
-    @property
-    def subscription_name(self) -> str:
-        """
-        Returns
-        -------
-        Name of the subscription
-        """
-        return self._root_name
-
-
 # Disable for proper docstring formatting
 # pylint: disable=line-too-long
-class Overrides(OverridesVariables):
+class Overrides(DictFormatterValidator):
     """
     Optional. This section allows you to define variables that can be used in any string formatter.
     For example, if you want your file and thumbnail files to match without copy-pasting a large
@@ -188,6 +153,16 @@ class Overrides(OverridesVariables):
 
     # pylint: enable=line-too-long
 
+    def _add_override_variable(self, key_name: str, format_string: str, sanitize: bool = False):
+        if sanitize:
+            key_name = f"{key_name}_sanitized"
+            format_string = sanitize_filename(format_string)
+
+        self._value[key_name] = StringFormatterValidator(
+            name="__should_never_fail__",
+            value=format_string,
+        )
+
     def __init__(self, name, value):
         super().__init__(name, value)
 
@@ -199,6 +174,23 @@ def __init__(self, name, value):
                 sanitize=True,
             )
 
+        if SUBSCRIPTION_NAME not in self._value:
+            for sanitized in [True, False]:
+                self._add_override_variable(
+                    key_name=SUBSCRIPTION_NAME,
+                    format_string=self.subscription_name,
+                    sanitize=sanitized,
+                )
+
+    @property
+    def subscription_name(self) -> str:
+        """
+        Returns
+        -------
+        Name of the subscription
+        """
+        return self._root_name
+
     def apply_formatter(
         self,
         formatter: StringFormatterValidator,