feat(docs): clarify TLS version requirements, fixes #343

docs/dyndns/update-api.rst

@@ -6,6 +6,11 @@ works.  We provide this API to be compatible with
 most dynDNS clients. However, we also provide a RESTful API that is
 more powerful and always preferred over the legacy interface described here.
 
+Please note that when using HTTPS (which we highly recommend), outdated setups
+(such as TLS < 1.2) are not supported.  If you encounter SSL/TLS handshake
+issues, you may have to update your dynDNS client and/or libraries used by it
+(such as OpenSSL).
+
 Update Request
 ``````````````
 An IP updates is performed by sending a GET request to ``update.dedyn.io`` via

docs/index.rst

@@ -6,10 +6,12 @@ information.  The interface design aims for simplicity so that tasks such as
 creating domains and manipulating DNS records can be handled with ease and in
 an intuitive fashion.
 
-Server-side operations, such as creation of domains or DNS records, expect
-JSON-formatted user input in the body of the ``POST``, ``PATCH``, or ``PUT``
-request (see below).  The request is required to come with a ``Content-Type:
-application/json`` header field.
+Server-side operations, such as creation of domains or DNS records, generally
+expect JSON-formatted user input in the body of the ``POST``, ``PATCH``, or
+``PUT`` request (see below).  Unless otherwise documented, requests are
+expected to come with a ``Content-Type: application/json`` header field and to
+be sent via HTTPS using state-of-the-art encryption. (Outdated setups, e.g.
+TLS < 1.2, are not supported.)
 
 API functionality is demonstrated using the command line tool ``curl``.  To
 pretty-print JSON output, process the data through ``jq``:  ``curl ... | jq .``.