chore(docs): Improve readme

Author: alukach

README.md

@@ -1,24 +1,66 @@
 # pydantic-ssm-settings
 
-Replace Pydantic's builtin [Secret Support](https://pydantic-docs.helpmanual.io/usage/settings/#secret-support) with a configuration provider that loads parameters from [AWS Systems Manager Parameter Store](https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-parameter-store.html). Parameters are loaded _lazily_, meaning that they are only requested from AWS if they are not provided via [standard field value priority](https://pydantic-docs.helpmanual.io/usage/settings/#field-value-priority) (i.e. initialiser, environment variable, or via `.env` file).
+Integrate [AWS Systems Manager Parameter Store](https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-parameter-store.html) with [Pydantic Settings](https://github.com/pydantic/pydantic-settings).
 
 ## Usage
 
-The simplest way to use this module is to inhert your settings `Config` class from `AwsSsmSourceConfig`. This will overwrite the [`file_secret_settings` settings source](https://pydantic-docs.helpmanual.io/usage/settings/#customise-settings-sources) with the `AwsSsmSettingsSource`. Provide a prefix to SSM parameters via the `_secrets_dir` initialiser value or the `secrets_dir` Config value.
+The simplest way to use this module is to inhert your settings from `SsmBaseSettings`. This add the `SsmSettingsSource` as a custom settings source and enabled passing source configuration (e.g. `_ssm_prefix`, `_ssm_client`) via `kwargs` when initializing a settings class.
 
 ```py
-from pydantic import BaseSettings
-from pydantic_ssm_settings import AwsSsmSourceConfig
+from pydantic_ssm_settings import SsmBaseSettings
 
 
-class WebserviceSettings(BaseSettings):
+class WebserviceSettings(SsmBaseSettings):
     some_val: str
     another_val: int
 
-    class Config(AwsSsmSourceConfig):
-        ...
+WebserviceSettings(_ssm_prefix="/prod/webservice")
+```
+
+Alternatively, configuration may be specified within the settings class via [`BaseModel.model_config`](https://docs.pydantic.dev/latest/api/base_model/#pydantic.BaseModel.model_config):
+
+```py
+from pydantic_ssm_settings import SsmSettingsConfigDict
+
+class WebserviceSettings(SsmBaseSettings):
+    model_config = SsmSettingsConfigDict(ssm_prefix="/prod/webservice")
+    some_val: str
+    another_val: int
 
-SimpleSettings(_secrets_dir='/prod/webservice')
+
+WebserviceSettings()
 ```
 
-The above example will attempt to retreive values from `/prod/webservice/some_val` and `/prod/webservice/another_val` if not provided otherwise.
+If it is preferred to avoid altering the baseclass of a settings model, the source can be manually added and configured as such:
+
+```py
+from typing import Tuple, Type
+from pydantic_settings import (
+    BaseSettings,
+    EnvSettingsSource,
+    InitSettingsSource,
+    PydanticBaseSettingsSource,
+    SecretsSettingsSource,
+)
+from pydantic_ssm_settings import SsmSettingsConfigDict, SsmSettingsSource
+
+class WebserviceSettings(BaseSettings):
+    model_config = SsmSettingsConfigDict(ssm_prefix="/asdf")
+    foo: str
+
+    def settings_customise_sources(
+        self,
+        settings_cls: Type[BaseSettings],
+        init_settings: InitSettingsSource,
+        env_settings: EnvSettingsSource,
+        dotenv_settings: PydanticBaseSettingsSource,
+        file_secret_settings: SecretsSettingsSource,
+    ) -> Tuple[PydanticBaseSettingsSource, ...]:
+        return (
+            init_settings,
+            env_settings,
+            dotenv_settings,
+            file_secret_settings,
+            SsmSettingsSource(settings_cls),
+        )
+```