devel/schemata: describe version 4

Replace numeric errors with human readable flags.  Not all sig_error
keys will necessarily be generated with a given version of gmime.

Drop status "none" as it's currrently unused and I don't know what
it's for.

devel/schemata

@@ -14,7 +14,7 @@ are interleaved. Keys are printed as keywords (symbols preceded by a
 colon), e.g. (:id "123" :time 54321 :from "foobar"). Null is printed as
 nil, true as t and false as nil.
 
-This is version 2 of the structured output format.
+This is version 4 of the structured output format.
 
 Version history
 ---------------
@@ -30,6 +30,10 @@ v3
 - Replaced message.filename string with a list of filenames.
 - Added part.content-disposition field.
 
+v4
+- replace signature error integer bitmask with a set of flags for
+  individual errors.
+
 Common non-terminals
 --------------------
 
@@ -121,7 +125,7 @@ sigstatus = [signature*]
 
 signature = {
     # (signature_status_to_string)
-    status:         "none"|"good"|"bad"|"error"|"unknown",
+    status:         "good"|"bad"|"error"|"unknown",
     # if status is "good":
     fingerprint?:   string,
     created?:       unix_time,
@@ -129,8 +133,20 @@ signature = {
     userid?:        string
     # if status is not "good":
     keyid?:         string
-    # if the signature has errors:
-    errors?:        int
+    errors?: 	    sig_errors
+}
+
+sig_errors = {
+    key-revoked?: bool,
+    key-expired?: bool,
+    sig-expired?: bool,
+    key-missing?: bool,
+    alg-unsupported?: bool,
+    crl-missing?: bool,
+    crl-too-old?: bool,
+    bad-policy?: bool,
+    sys-error?: bool,
+    tofu-conflict?: bool
 }
 
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