Add defaults for LDO schemas

While it no longer makes sense to have a universal default schema
value (see previous commit), the LDO schema keywords have specific
implications which do match one or the other boolean schema.

This commit adds the appropraite one.  By default, a resource is
assumed to provide or accept any structure as its representation,
accept any structure for processing if it does processing at all,
and to allow any header usage.  So targetSchema, submissionSchema,
and headerSchema all default to true.

However, by default, URI templates may not be resolved from input,
so headerSchema defaults to false.

Author: handrews

links.json

@@ -29,7 +29,8 @@
                     "format": "uri-template"
                 },
                 "hrefSchema": {
-                    "$ref": "http://json-schema.org/draft-08/hyper-schema#"
+                    "$ref": "http://json-schema.org/draft-08/hyper-schema#",
+                    "default": false
                 },
                 "templatePointers": {
                     "type": "object",
@@ -55,21 +56,24 @@
                     "type": "string"
                 },
                 "targetSchema": {
-                    "$ref": "http://json-schema.org/draft-08/hyper-schema#"
+                    "$ref": "http://json-schema.org/draft-08/hyper-schema#",
+                    "default": true
                 },
                 "targetMediaType": {
                     "type": "string"
                 },
                 "targetHints": { },
                 "headerSchema": {
-                    "$ref": "http://json-schema.org/draft-08/hyper-schema#"
+                    "$ref": "http://json-schema.org/draft-08/hyper-schema#",
+                    "default": true
                 },
                 "submissionMediaType": {
                     "type": "string",
                     "default": "application/json"
                 },
                 "submissionSchema": {
-                    "$ref": "http://json-schema.org/draft-08/hyper-schema#"
+                    "$ref": "http://json-schema.org/draft-08/hyper-schema#",
+                    "default": true
                 },
                 "$comment": {
                     "type": "string"