Introduce OpenAPI specs (#4351)

* wip

* wip

* wip

* Update index.ts

* Update gen-openapi-spec.ts

* Update api.ja-JP.md

* Fix

* Improve doc

* Update gen-openapi-spec.ts

* Update redoc.html

* Improve doc

* Update gen-openapi-spec.ts

* Improve doc

* Update CHANGELOG.md

src/server/api/endpoints/auth/accept.ts

@@ -8,6 +8,8 @@ import define from '../../define';
 import { ApiError } from '../../error';
 
 export const meta = {
+	tags: ['auth'],
+
 	requireCredential: true,
 
 	secure: true,

src/server/api/endpoints/auth/session/generate.ts

@@ -7,6 +7,8 @@ import define from '../../../define';
 import { ApiError } from '../../../error';
 
 export const meta = {
+	tags: ['auth'],
+
 	requireCredential: false,
 
 	params: {

src/server/api/endpoints/auth/session/show.ts

@@ -4,6 +4,8 @@ import define from '../../../define';
 import { ApiError } from '../../../error';
 
 export const meta = {
+	tags: ['auth'],
+
 	requireCredential: false,
 
 	params: {

src/server/api/endpoints/auth/session/userkey.ts

@@ -7,6 +7,8 @@ import define from '../../../define';
 import { ApiError } from '../../../error';
 
 export const meta = {
+	tags: ['auth'],
+
 	requireCredential: false,
 
 	params: {