Replace context with api.

This keeps the user logged in after tab closing, since state is stored in the server.

src/components/Auth/SignUpForm/SeniorType.ts

+export type SeniorType = {
+  username: string;
+  password: string;
+  firstName: string;
+  lastName: string;
+  email: string;
+  phoneNumber: number;
+  address: number;
+  name: string;
+  memberCardNumber: number;
+  notes: string;
+};