Adopt Erlfmt (#33)

This is an attempt to define some consistent formatting rules for our Erlang code.

I made some research and I tested various options, so far the one that I prefer is [erlfmt](https://github.com/WhatsApp/erlfmt) from WhatsApp. Like most non-builtin formatters, this is opinionated. But the choices they made are well thought, and seem to be a good starting point.


You have both the option to reformat the code inline:

```
rebar3 fmt
```

or check the formatting:

```
rebar3 fmt --check
```

This last command is especially useful for CI integration.

include/dns_records.hrl

@@ -2,34 +2,40 @@
 -define('__dns_records.hrl__', ok).
 -include("dns_terms.hrl").
 
--record(dns_message, {id = dns:random_id() :: dns:message_id(),
-		      qr = false :: 0..1 | boolean(),
-		      oc = ?DNS_OPCODE_QUERY :: dns:opcode(),
-		      aa = false :: 0..1 | boolean(),
-		      tc = false :: 0..1 | boolean(),
-		      rd = false :: 0..1 | boolean(),
-		      ra = false :: 0..1 | boolean(),
-		      ad = false :: 0..1 | boolean(),
-		      cd = false :: 0..1 | boolean(),
-		      rc = ?DNS_RCODE_NOERROR :: dns:rcode(),
-		      qc = 0 :: 0..65535,
-		      anc = 0 :: 0..65535,
-		      auc = 0 :: 0..65535,
-		      adc = 0 :: 0..65535,
-		      questions = [] :: dns:questions(),
-		      answers = [] :: dns:answers(),
-		      authority = [] :: dns:authority(),
-		      additional = [] :: dns:additional()}).
+-record(dns_message, {
+    id = dns:random_id() :: dns:message_id(),
+    qr = false :: 0..1 | boolean(),
+    oc = ?DNS_OPCODE_QUERY :: dns:opcode(),
+    aa = false :: 0..1 | boolean(),
+    tc = false :: 0..1 | boolean(),
+    rd = false :: 0..1 | boolean(),
+    ra = false :: 0..1 | boolean(),
+    ad = false :: 0..1 | boolean(),
+    cd = false :: 0..1 | boolean(),
+    rc = ?DNS_RCODE_NOERROR :: dns:rcode(),
+    qc = 0 :: 0..65535,
+    anc = 0 :: 0..65535,
+    auc = 0 :: 0..65535,
+    adc = 0 :: 0..65535,
+    questions = [] :: dns:questions(),
+    answers = [] :: dns:answers(),
+    authority = [] :: dns:authority(),
+    additional = [] :: dns:additional()
+}).
 
--record(dns_query, {name :: dns:dname(),
-		    class = ?DNS_CLASS_IN :: dns:class(),
-		    type :: dns:type()}).
+-record(dns_query, {
+    name :: dns:dname(),
+    class = ?DNS_CLASS_IN :: dns:class(),
+    type :: dns:type()
+}).
 
--record(dns_rr, {name :: dns:dname(),
-		 class = ?DNS_CLASS_IN :: dns:class(),
-		 type :: dns:type(),
-		 ttl = 0 :: dns:ttl(),
-		 data :: dns:rrdata()}).
+-record(dns_rr, {
+    name :: dns:dname(),
+    class = ?DNS_CLASS_IN :: dns:class(),
+    type :: dns:type(),
+    ttl = 0 :: dns:ttl(),
+    data :: dns:rrdata()
+}).
 -record(dns_rrdata_a, {ip}).
 -record(dns_rrdata_aaaa, {ip}).
 -record(dns_rrdata_afsdb, {subtype, hostname}).
@@ -45,10 +51,12 @@
 -record(dns_rrdata_cds, {keytag, alg, digest_type, digest}).
 -record(dns_rrdata_hinfo, {cpu, os}).
 -record(dns_rrdata_https, {svc_priority, target_name, svc_params}).
--record(dns_rrdata_ipseckey, {precedence,
-			      alg,
-			      gateway,
-			      public_key}).
+-record(dns_rrdata_ipseckey, {
+    precedence,
+    alg,
+    gateway,
+    public_key
+}).
 -record(dns_rrdata_key, {type, xt, name_type, sig, protocol, alg, public_key}).
 -record(dns_rrdata_kx, {preference, exchange}).
 -record(dns_rrdata_loc, {size, horiz, vert, lat, lon, alt}).
@@ -57,58 +65,66 @@
 -record(dns_rrdata_minfo, {rmailbx, emailbx}).
 -record(dns_rrdata_mr, {newname}).
 -record(dns_rrdata_mx, {preference, exchange}).
--record(dns_rrdata_naptr, {order,
-			   preference,
-			   flags,
-			   services,
-			   regexp,
-			   replacement}).
+-record(dns_rrdata_naptr, {
+    order,
+    preference,
+    flags,
+    services,
+    regexp,
+    replacement
+}).
 -record(dns_rrdata_ns, {dname}).
 -record(dns_rrdata_nsec, {next_dname, types}).
 -record(dns_rrdata_nsec3, {hash_alg, opt_out, iterations, salt, hash, types}).
 -record(dns_rrdata_nsec3param, {hash_alg, flags, iterations, salt}).
 -record(dns_rrdata_nxt, {dname, types}).
 -record(dns_rrdata_ptr, {dname}).
 -record(dns_rrdata_rp, {mbox, txt}).
--record(dns_rrdata_rrsig, {type_covered,
-			   alg,
-			   labels,
-			   original_ttl,
-			   expiration,
-			   inception,
-			   key_tag,
-			   signers_name,
-			   signature}).
+-record(dns_rrdata_rrsig, {
+    type_covered,
+    alg,
+    labels,
+    original_ttl,
+    expiration,
+    inception,
+    key_tag,
+    signers_name,
+    signature
+}).
 -record(dns_rrdata_rt, {preference, host}).
--record(dns_rrdata_soa, {mname,
-			 rname,
-			 serial,
-			 refresh,
-			 retry,
-			 expire,
-			 minimum}).
+-record(dns_rrdata_soa, {
+    mname,
+    rname,
+    serial,
+    refresh,
+    retry,
+    expire,
+    minimum
+}).
 -record(dns_rrdata_spf, {spf}).
 -record(dns_rrdata_srv, {priority, weight, port, target}).
 -record(dns_rrdata_sshfp, {alg, fp_type, fp}).
 -record(dns_rrdata_svcb, {svc_priority, target_name, svc_params}).
 -record(dns_rrdata_tsig, {alg, time, fudge, mac, msgid, err, other}).
 -record(dns_rrdata_txt, {txt}).
 
--record(dns_optrr, {udp_payload_size = 4096,
-		    ext_rcode = ?DNS_ERCODE_NOERROR,
-		    version = 0,
-		    dnssec = false,
-		    data = []}).
+-record(dns_optrr, {
+    udp_payload_size = 4096,
+    ext_rcode = ?DNS_ERCODE_NOERROR,
+    version = 0,
+    dnssec = false,
+    data = []
+}).
 -record(dns_opt_llq, {opcode, errorcode, id, leaselife}).
 -record(dns_opt_nsid, {data}).
 -record(dns_opt_owner, {seq = 0, primary_mac, wakeup_mac, password}).
 -record(dns_opt_ul, {lease}).
 -record(dns_opt_ecs, {
-		      family,
-		      source_prefix_length, 
-		      scope_prefix_length,
-		      address
-		     }).
+    family,
+    source_prefix_length,
+    scope_prefix_length,
+    address
+}).
 -record(dns_opt_unknown, {id, bin}).
 
 -endif.