chore: token api simplification (#4600)

## About the changes
We found a problem generating the Go SDK client for the tokens API that
makes use of `oneOf`, combined with `allOf`. The generator doesn't know
how to map this type and leaves it as an object. This PR simplifies the spec and therefore the code generated after it

src/lib/openapi/spec/create-api-token-schema.ts

@@ -1,5 +1,5 @@
 import { FromSchema } from 'json-schema-to-ts';
-
+import { mergeAllOfs } from '../util/all-of';
 const adminSchema = {
     required: ['type'],
     type: 'object',
@@ -74,6 +74,18 @@ const clientFrontendSchema = {
     },
 } as const;
 
+const expireSchema = {
+    type: 'object',
+    properties: {
+        expiresAt: {
+            type: 'string',
+            format: 'date-time',
+            description: 'The time when this token should expire.',
+            example: '2023-07-04T11:26:24+02:00',
+        },
+    },
+} as const;
+
 // TODO: (openapi) this schema isn't entirely correct: `project` and `projects`
 // are mutually exclusive.
 //
@@ -88,27 +100,11 @@ export const createApiTokenSchema = {
     type: 'object',
     description:
         'The data required to create an [Unleash API token](https://docs.getunleash.io/reference/api-tokens-and-client-keys).',
-    properties: {
-        expiresAt: {
-            type: 'string',
-            format: 'date-time',
-            description: 'The time when this token should expire.',
-            example: '2023-07-04T11:26:24+02:00',
-        },
-    },
     oneOf: [
-        {
-            allOf: [adminSchema, tokenNameSchema],
-        },
-        {
-            allOf: [adminSchema, usernameSchema],
-        },
-        {
-            allOf: [clientFrontendSchema, tokenNameSchema],
-        },
-        {
-            allOf: [clientFrontendSchema, usernameSchema],
-        },
+        mergeAllOfs([expireSchema, adminSchema, tokenNameSchema]),
+        mergeAllOfs([expireSchema, adminSchema, usernameSchema]),
+        mergeAllOfs([expireSchema, clientFrontendSchema, tokenNameSchema]),
+        mergeAllOfs([expireSchema, clientFrontendSchema, usernameSchema]),
     ],
     components: {},
 } as const;

src/lib/openapi/util/all-of.ts

@@ -0,0 +1,43 @@
+import { JSONSchema } from 'json-schema-to-ts';
+
+// this function simplifies simple schemas and return allOf schema if it
+// doesn't know how to simplify it. It's a proof of concept but it can be extended
+export function mergeAllOf(a: JSONSchema, b: JSONSchema): JSONSchema {
+    if (typeof a !== 'boolean' && typeof b !== 'boolean') {
+        const {
+            required: aRequired,
+            properties: aProperties,
+            type: aType,
+            ...aRest
+        } = a;
+        const {
+            required: bRequired,
+            properties: bProperties,
+            type: bType,
+            ...bRest
+        } = b;
+        if (
+            Object.keys(aRest).length === 0 &&
+            Object.keys(bRest).length === 0 &&
+            aType === 'object' &&
+            bType === 'object'
+        ) {
+            return {
+                required: [...(aRequired ?? []), ...(bRequired ?? [])],
+                type: 'object',
+                properties: { ...aProperties, ...bProperties },
+            };
+        }
+    }
+    return {
+        allOf: [a, b],
+    };
+}
+
+export function mergeAllOfs(schemas: JSONSchema[]): JSONSchema {
+    if (schemas.length === 1) {
+        return schemas[0];
+    }
+    const [a, b, ...rest] = schemas;
+    return mergeAllOfs([mergeAllOf(a, b), ...rest]);
+}