Make the internal helper types of the typings internal

doc/release-notes/changelog.md

@@ -32,6 +32,7 @@
 - `insertGraph()`, `upsertGraph()` and their `*AndFetch()` variants throw an error for unknown graph options like `noInset` instead of ignoring them with a warning, and `insertGraph()` also for the options of `upsertGraph()` that have no effect on an insert, like `noDelete` or `allowMarkers`. See [migration](/release-notes/migration.md#unknown-graph-options-throw) [#84](https://github.com/ditojs/objection/issues/84)
 - The type parameter of `RelateQueryBuilder` is the number query builder, e.g. `RelateQueryBuilder<NumberQueryBuilder<this>>` in custom query builders that override `relate()`. See [migration](/release-notes/migration.md#typescript-relatequerybuilder-takes-the-number-query-builder)
 - Custom query builders declare one `RebindType` member instead of the five `ArrayQueryBuilderType`, `SingleQueryBuilderType`, `MaybeSingleQueryBuilderType`, `NumberQueryBuilderType` and `PageQueryBuilderType` members, which are removed: `declare RebindType: MyQueryBuilder<this['~M'], this['~R'], this['~X']>`, with the extra types `X` as third type parameter. The helper types `SingleQueryBuilder<QB>` etc. take a query builder, and `WithGraphModelQueryBuilder` and `ReturningMethod` are removed. See [migration](/release-notes/migration.md#typescript-custom-query-builders-declare-rebindtype) [#125](https://github.com/ditojs/objection/issues/125) [#319](https://github.com/Vincit/objection.js/issues/319)
+- The internal helper types of the relation expression parser, the `withGraph*()` narrowing and the property names, like `ParseRelationString`, `WithGraph` and `RelationPropertyNames`, are no longer exported, and the unused `ItemType` is removed. See [migration](/release-notes/migration.md#typescript-internal-helper-types-are-no-longer-exported)
 - `static jsonSchema` is typed `ReadonlyJSONSchema`, a JSON schema with readonly arrays, so that it takes schemas declared `as const`. A model's schema read through the static type can't be passed where a `JSONSchema` is expected, unless the model declares `static jsonSchema: JSONSchema`. See [migration](/release-notes/migration.md#typescript-model-jsonschema-is-a-readonly-schema) [#16](https://github.com/ditojs/objection/issues/16)
 - `insert()`, `patch()`, `update()`, their `*AndFetch*()` and `*ById()` variants, `merge()` and `relate()` reject relation properties, which they ignore at runtime: they take a `PartialModelRow<M>`, a model instance or its properties without relations, instead of `PartialModelObject<M>`. Values whose type includes the relation properties are rejected too, e.g. `Partial<M>`, `ModelObject<M>` or `PartialModelObject<M>` of models with relations. `insertGraph()` and `upsertGraph()` take relations. See [migration](/release-notes/migration.md#typescript-insert-patch-and-update-reject-relation-data) [#53](https://github.com/ditojs/objection/issues/53)
 - `distinctOn()` is typed to take column names, `raw()` and `ref()`, like `groupBy()`, instead of any selection, as it doesn't select its columns.

doc/release-notes/migration.md

@@ -35,6 +35,7 @@ This section lists the breaking changes in objection 4.0.
 - [typescript: insertGraph() has no allowMarkers option](#typescript-insertgraph-has-no-allowmarkers-option)
 - [typescript: RelateQueryBuilder takes the number query builder](#typescript-relatequerybuilder-takes-the-number-query-builder)
 - [typescript: Custom query builders declare RebindType](#typescript-custom-query-builders-declare-rebindtype)
+- [typescript: Internal helper types are no longer exported](#typescript-internal-helper-types-are-no-longer-exported)
 - [typescript: Model.jsonSchema is a readonly schema](#typescript-model-jsonschema-is-a-readonly-schema)
 - [typescript: insert(), patch() and update() reject relation data](#typescript-insert-patch-and-update-reject-relation-data)
 - [typescript: Property types leave out $ properties](#typescript-property-types-leave-out-properties)
@@ -370,6 +371,10 @@ The third type parameter `X` holds extra types of the query, which strict mode u
 
 The helper types `SingleQueryBuilder`, `MaybeSingleQueryBuilder`, `ArrayQueryBuilder`, `NumberQueryBuilder` and `PageQueryBuilder` take any query builder, e.g. `MaybeSingleQueryBuilder<this>` as the return type of an overridden `findById()`, and `NumberQueryBuilder<MaybeSingleQueryBuilder<this>>` for `patchById()`, `updateById()` and `deleteById()`, the writes of `findById()`. `WithGraphModelQueryBuilder<M, E>` is removed. Use `QueryBuilderType<WithGraphModel<M, E>>` instead. The `ReturningMethod` interface is removed too, `returning()` is a method of `QueryBuilder`. On query builders with an `any` result, e.g. `AnyQueryBuilder`, it returns `QueryBuilder<any, any> | QueryBuilder<any, any[]>` instead of `QueryBuilder<any, any[]>`.
 
+## typescript: Internal helper types are no longer exported
+
+The helper types of the relation expression parser, the `withGraph*()` narrowing and the property names, like `ParseRelationString`, `WithGraph`, `WithGraphProperty`, `InsertablePropertyNames` and `RelationPropertyNames`, are no longer exported, and the unused `ItemType` is removed. Use `WithGraphModel`, `WithGraphQueryBuilder`, `ModelProps` and `ModelRelations` instead.
+
 ## typescript: Model.jsonSchema is a readonly schema
 
 `static jsonSchema` is typed `ReadonlyJSONSchema`, a JSON schema with readonly arrays, so that schemas declared `as const` can be assigned to it, for `FromJSONSchema`. A `JSONSchema` is assignable to it, but not the other way around: a model's schema read through the static type can't be passed to a parameter typed `JSONSchema`, or returned from `$beforeValidate()`. Declare the type on models that are used that way: