Update the documentation to include new environment keys

Author: Jaspaul

readme.md

@@ -33,12 +33,23 @@ php artisan vendor:publish
 You will need to set the following details in your environment:
 
 ```sh
+SIGNED_REQUEST_ALGORITHM=
+SIGNED_REQUEST_CACHE_PREFIX=
 SIGNED_REQUEST_SIGNATURE_HEADER=
 SIGNED_REQUEST_ALGORITHM_HEADER=
 SIGNED_REQUEST_KEY=
+SIGNED_REQUEST_ALLOW_REPLAYS=
+SIGNED_REQUEST_TOLERANCE_SECONDS=
 ```
 
-The `SIGNED_REQUEST_SIGNATURE_HEADER` should be the request header that the signature will be included on, something like `X-SIGNATURE`. Similarly the `SIGNED_REQUEST_ALGORITHM_HEADER` should be the request header that the includes the algorithm used to sign the request. Finally the `SIGNED_REQUEST_KEY` should hold the key used to verify the signed requests.
+Each of the settings above allows for a different level of configuration.
+    - `SIGNED_REQUEST_ALGORITHM` is the algorithm that will be used to generate / verify the signature. This is defaulted to use `sha256` feel free to change this to anything that `hash_hmac` accepts.
+    - `SIGNED_REQUEST_CACHE_PREFIX` is the prefix to use for all the cache keys that will be generated. Here you can use the default if you're not planning on sharing a cache between multiple applications.
+    - `SIGNED_REQUEST_SIGNATURE_HEADER` should be the request header that the signature will be included on, `X-Signature` will be used by default.
+    - `SIGNED_REQUEST_ALGORITHM_HEADER` should be the request header that the includes the algorithm used to sign the request.
+    - `SIGNED_REQUEST_KEY` is the shared secret key between the application generating the requests, and the application consuming them. This value should not be publically available.
+    - `SIGNED_REQUEST_ALLOW_REPLAYS` allows you to enable or disable replay attacks. By default replays are disabled.
+    - `SIGNED_REQUEST_TOLERANCE_SECONDS` is the number of seconds that a request will be considered for. This setting allows for some time drift between servers and is only used when replays are disabled.
 
 ### Setup the Middleware