diameter: default port and transport for DiameterURI

[wmnsk]

This PR consists of two commits;

• diameter: DiameterURI port defaults to 3868

This fixes the crash when decoding a DiameterURI without a port number. The crash always happens if an Diameter answer with an AVP of type DiameterURI without port number is decoded, since the rfc option cannot be specified when handling an answer.

• diameter: DiameterURI transport defaults to tcp

When rfc is missing in the option, the transport part of the diameter_uri becomes an empty atom (''), which causes the diameter module to fail to re-encode the decoded AVP (because it won't match diameter_types:'DiameterURI'/3 properly).

This sets tcp as the default transport as described in RFC6733 instead of leaving it empty.

Some notes/thoughts;

• The first clause (portnr(<<>>, aaa, #{rfc := 6733}), transport(<<>>, #{rfc := 6733})) can be removed if it's preferable.
• This can be tested by removing rfc => 6733 from diameter_codec_test:opts. I have no idea how to add a case for this.
• Perhaps adding rfc => 6733 in the decode option by default is another way to solve this, but it may require wider consideration.

Please advise 🙂

Debug log w/ redbug:

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:'DiameterURI'(decode, <<"aaa://ims.foo.com">>, #{app_dictionary => dia_3gpp_Cx,decode_format => map,failed_avp => false,
  incoming_maxlen => 16777215,module => dia_3gpp,
  restrict_connections => nodes,
  sequence => {0,28},
  share_peers => false,spawn_opt => [],strict_arities => false,
  strict_mbit => true,string_decode => false,traffic_counters => true,
  use_shared_peers => false})

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:scan_uri(<<"aaa://ims.foo.com">>, #{app_dictionary => dia_3gpp_Cx,decode_format => map,failed_avp => false,
  incoming_maxlen => 16777215,module => dia_3gpp,
  restrict_connections => nodes,
  sequence => {0,28},
  share_peers => false,spawn_opt => [],strict_arities => false,
  strict_mbit => true,string_decode => false,traffic_counters => true,
  use_shared_peers => false})

% 13:46:05.976 <0.32401.513>(dead)
% re:run(<<"aaa://ims.foo.com">>, "^(aaas?)://([-a-zA-Z0-9.]{1,255})(:0{0,5}([0-9]{1,5}))?(;transport=(tcp|sctp|udp))?(;protocol=(diameter|radius|tacacs\\+))?$", [{capture,[1,2,4,6,8],binary}])

% 13:46:05.976 <0.32401.513>(dead)
% re:run/3 -> {match,[<<"aaa">>,<<"ims.foo.com">>,<<>>,<<>>,<<>>]}

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:to_atom(<<"aaa">>)

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:to_atom/1 -> aaa

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:portnr(<<>>, aaa, #{app_dictionary => dia_3gpp_Cx,decode_format => map,failed_avp => false,
  incoming_maxlen => 16777215,module => dia_3gpp,
  restrict_connections => nodes,
  sequence => {0,28},
  share_peers => false,spawn_opt => [],strict_arities => false,
  strict_mbit => true,string_decode => false,traffic_counters => true,
  use_shared_peers => false})

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:portnr/3 -> {error,badarg}

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:scan_uri/2 -> {error,badarg}

% 13:46:05.976 <0.32401.513>(dead)
% diameter_types:'DiameterURI'/3 -> {error,badarg}

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CT Test Results

  2 files   34 suites   13m 8s ⏱️
132 tests 129 ✅ 3 💤 0 ❌
160 runs  157 ✅ 3 💤 0 ❌

Results for commit d69f935.

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