add createSubscription

src/schema.gql

@@ -883,6 +883,7 @@ type Mutation {
   unfollowUser(followedUserId: Int!): UserGQL!
   retireTags(tagIds: [Int!]!): Boolean!
   ensureStripeCustomerExists: UserGQL!
+  createSubscription(priceId: String!): CreateSubscriptionResultGQL!
   findPrerecordTableLayout(b64Image: String!, videoId: Int!): HomographyInfoGQL
   createUploadStream(
     videoMetadata: VideoMetadataInput!
@@ -992,6 +993,11 @@ input EditUserInputGQL {
   videosPrivateByDefault: Boolean = null
 }
 
+type CreateSubscriptionResultGQL {
+  checkoutUrl: String!
+  sessionId: String!
+}
+
 type CreateUploadStreamReturn {
   videoId: Int!
 }