Use "discriminating value" consistently

I found the "discriminator value" language confusing, because
`discriminator` is the field name, and in most cases the value
of a field is the value in the OpenAPI Description.

Reviewers did not like "discriminator property value", but
"discriminating value" makes it clear that this is about the
value that actually causes schema selection, and not about
the value of the discriminator keyword.

Also removed placeholder in favor of just having the headings,
as has been done in several other PRs that overlap with
new section PRs for internal linking.

Author: handrews

versions/3.0.4.md

@@ -165,8 +165,6 @@ If the same JSON/YAML object is parsed multiple times and the respective context
 
 #### <a name="resolvingImplicitConnections"></a>Resolving Implicit Connections
 
-***TODO: In another PR***
-
 ### <a name="dataTypes"></a>Data Types
 
 Primitive data types in the OAS are based on the types supported by the [JSON Schema Specification Wright Draft 00](https://tools.ietf.org/html/draft-wright-json-schema-00#section-4.2). 
@@ -2648,7 +2646,7 @@ components:
         ]
       },
       "Cat": {
-        "description": "A representation of a cat. Note that `Cat` will be used as the discriminator value.",
+        "description": "A representation of a cat. Note that `Cat` will be used as the discriminating value.",
         "allOf": [
           {
             "$ref": "#/components/schemas/Pet"
@@ -2675,7 +2673,7 @@ components:
         ]
       },
       "Dog": {
-        "description": "A representation of a dog. Note that `Dog` will be used as the discriminator value.",
+        "description": "A representation of a dog. Note that `Dog` will be used as the discriminating value.",
         "allOf": [
           {
             "$ref": "#/components/schemas/Pet"
@@ -2717,7 +2715,7 @@ components:
       required:
       - name
       - petType
-    Cat:  # "Cat" will be used as the discriminator value
+    Cat:  # "Cat" will be used as the discriminating value
       description: A representation of a cat
       allOf:
       - $ref: '#/components/schemas/Pet'
@@ -2733,7 +2731,7 @@ components:
             - aggressive
         required:
         - huntingSkill
-    Dog:  # "Dog" will be used as the discriminator value
+    Dog:  # "Dog" will be used as the discriminating value
       description: A representation of a dog
       allOf:
       - $ref: '#/components/schemas/Pet'
@@ -2758,7 +2756,7 @@ The Discriminator Object does this by implicitly or explicitly associating the p
 ##### Fixed Fields
 Field Name | Type | Description
 ---|:---:|---
-<a name="propertyName"></a>propertyName | `string` | **REQUIRED**. The name of the property in the payload that will hold the discriminator value. This property SHOULD be required in the payload schema, as the behavior when the property is absent is undefined.
+<a name="propertyName"></a>propertyName | `string` | **REQUIRED**. The name of the property in the payload that will hold the discriminating value. This property SHOULD be required in the payload schema, as the behavior when the property is absent is undefined.
 <a name="discriminatorMapping"></a> mapping | Map[`string`, `string`] | An object to hold mappings between payload values and schema names or URI references.
 
 ##### Conditions for Using the Discriminator Object
@@ -2834,7 +2832,7 @@ MyResponseType:
       monster: https://gigantic-server.com/schemas/Monster/schema.json
 ```
 
-Here the discriminator property _value_ of `dog` will map to the schema `#/components/schemas/Dog`, rather than the default (implicit) value of `#/components/schemas/dog`.  If the discriminator property _value_ does not match an implicit or explicit mapping, no schema can be determined and validation SHOULD fail.
+Here the discriminating value of `dog` will map to the schema `#/components/schemas/Dog`, rather than the default (implicit) value of `#/components/schemas/dog`.  If the discriminating value does not match an implicit or explicit mapping, no schema can be determined and validation SHOULD fail.
 
 When used in conjunction with the `anyOf` construct, the use of the discriminator can avoid ambiguity where multiple schemas may satisfy a single payload.