Adjust Neo4j's currentUser to be more ergonomic

Typically, we don't need to bind it a query node name.
And this is even forbidden in "path exists" expressions.

So now
```ts
currentUser == "(:User { id: $currentUser })"
```

And if you need to bind it, you can:
```ts
currentUser.as('user') == "(user:User { id: $currentUser })"
```

Author: CarsonF

src/core/database/query/create-relationships.ts

@@ -107,6 +107,8 @@ export function createRelationships<TResourceStatic extends ResourceShape<any>>(
             variable: !Array.isArray(varOrTuple)
               ? varOrTuple instanceof Variable
                 ? varOrTuple.value
+                : currentUser.is(varOrTuple)
+                ? relLabel
                 : undefined
               : Array.isArray(varOrTuple[1])
               ? `${relLabel}${i}`
@@ -156,8 +158,8 @@ export function createRelationships<TResourceStatic extends ResourceShape<any>>(
             flattened.map(({ variable, nodeLabel, id }) =>
               id instanceof Variable
                 ? []
-                : id === currentUser
-                ? [currentUser]
+                : currentUser.is(id)
+                ? [id.as(variable!)]
                 : [node(variable, nodeLabel, { id })],
             ),
           )

src/core/database/query/matching.ts

@@ -19,9 +19,21 @@ import {
 import { variable } from '../query-augmentation/condition-variables';
 import { apoc, collect, listConcat, merge } from './cypher-functions';
 
-export const currentUser = node('currentUser', 'User', {
-  id: variable('$currentUser'),
-}) as Tagged<NodePattern, 'CurrentUser'>;
+const currentUserFlag = Symbol();
+const makeCurrentUser = (name: string) =>
+  Object.assign(
+    Object.defineProperty(
+      node(name, 'User', { id: variable('$currentUser') }),
+      currentUserFlag,
+      {},
+    ) as Tagged<NodePattern, 'CurrentUser'>,
+    {
+      as: makeCurrentUser,
+      is: (obj: object): obj is typeof currentUser =>
+        Object.hasOwn(obj, currentUserFlag),
+    },
+  );
+export const currentUser = makeCurrentUser('');
 
 export const requestingUser = (session?: Session | ID) => {
   const n = node('requestingUser', 'User', {