chore: rename middleware dirs

middleware/encrypted-payloads/README.md

@@ -0,0 +1,53 @@
+# Encrypted Request + Response Payloads Middleware
+
+Shows an example of a `from_fn` middleware that:
+
+1. extracts a JSON request payload;
+1. decrypts a data field;
+1. re-encodes as JSON and re-packs the request;
+1. calls the wrapped service;
+1. unpacks the response and parses a similarly structured JSON object;
+1. encrypts the data field;
+1. re-packs the response.
+
+All this to say, it provides a (fairly brittle) way to have handlers not need to care about the encryption and decryption steps.
+
+## Usage
+
+Using [HTTPie] throughout for simplicity.
+
+```console
+$ http POST :8080/encrypt id:=1234 data=abcde > tmp.json
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+    "id": 1234,
+    "data": "kq6MKdP+I0hoI7YC7CN39yamx67T",
+    "nonce": "dW5pcXVlIG5vbmNl"
+}
+
+$ cat tmp.json | http -v POST :8080/reverse
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+    "data": "UL4PeOr9Di8xpFEJZgylJ5K8R7vW",
+    "nonce": "dW5pcXVlIG5vbmNl"
+}
+```
+
+The server logs would look something like
+
+```plain
+[INFO  middleware_encrypted_payloads] creating encrypted sample request for ID = 1234
+[INFO  actix_web::middleware::logger] 127.0.0.1 "POST /encrypt HTTP/1.1" 200 76 "-" "-" 0.000393
+...
+[INFO  middleware_encrypted_payloads] decrypting request 1234
+[INFO  middleware_encrypted_payloads] request 1234 with data: abcde
+[INFO  middleware_encrypted_payloads] response 1234 with new data: edcba
+[INFO  middleware_encrypted_payloads] encrypting response 1234
+[INFO  actix_web::middleware::logger] 127.0.0.1 "POST /reverse HTTP/1.1" 200 66 "-" "-" 0.000425
+```
+
+[httpie]: https://httpie.io/cli