one to many relation ship in java spring boot

I have 2 tables Users and Institution, with primary keys respectively user_Id and institution_id.
Each user works at one and only one institution, although an institution can have many Users.
so its a one to many relation ship.
But in my mySQL db the institution table has a fixed number of institutions that the user can work in.
there is a foreign key of institution_Id in my user table that specifies which institution does he work for.
while adding the user using a rest api i can't specify which institution does he work for

-----user model-----

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="user_Id")
private int userId;
@Column(name="name")
private String name;
@Column(name="lastname")
private String lastname;
@Column(name="email")
private String email;
@Column(name="password")
private String password;
@Column(name="isActive")
private boolean isActive;
@Column(name="lastActive")
private String lastActive;
@Column(name="createdDate")
private String createdDate;
@Column(name="isBlocked")
private boolean isBlocked;
@ManyToOne(fetch = FetchType.LAZY, optional = false)
@JoinColumn(name = "institution_id", nullable = false)
private Institution institution;
@ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
@JoinTable(name = "user_has_role",
joinColumns = {
@JoinColumn(name = "user_id", referencedColumnName = "user_id",
nullable = false, updatable = true)},
inverseJoinColumns = {
@JoinColumn(name = "role_id", referencedColumnName = "role_id",
nullable = false, updatable = true)})
private Set<Role> roles = new HashSet<>();
} 

-------Institution model--------

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Entity
@Table(name = "institution")
public class Institution {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="institution_Id")
private int institutionId;
@Column(name="name")
private String name;
@Column(name="type")
private String type;
@Column(name="location")
private String location;
@OneToMany(mappedBy = "institution", fetch = FetchType.LAZY)
private Set<User> user;
}

------controller------
here im using api's to add users...

@GetMapping("/getAllUsers")
public List<User> getAllUsers() {
return (List<User>) userrepository.findAll();
}
@PostMapping("/addUser")
public String addUser(@RequestBody User user) {
userrepository.save(user);
return "user saved with name: " + user.getName();
}

is there a way to do it ?

--------the api request---------

{
"name" : "Jawad",
"lastname" : "Zakhour",
"email" : "jawadzakhour@hotmail.com",
"password" : "jawad123",
"isActive" : 0,
"lastActive" : "13/08/2020",
"createdDate" : "07/07/2020",
"isBlocked" : 0,
"institution" : 
{
"name" : "maliks",
"type" : "Merchant",
"location" : "Le mall sen el fil"
}
}

...

Thanks for adding details.
You can achieve the same by passing the primary key of the institution table which is institution_Id for the corresponding record.

For Example- If you want the user Jawad to be linked to the institution maliks, then your institution table should have a row inserted already with values as maliks, Merchant, Le mall sen el fil for name, type and location columns respectively. (I am assuming this recod has institution_Id = 1 in your DB)

Then you need to pass the below JSON as request

{
"name" : "Jawad",
"lastname" : "Zakhour",
"email" : "jawadzakhour@hotmail.com",
"password" : "jawad123",
"isActive" : 0,
"lastActive" : "13/08/2020",
"createdDate" : "07/07/2020",
"isBlocked" : 0,
"institution" : 
{
"institutionId" : 1  // As per my assumption stated above
}
}

Another thing you need to make sure is your User model has cascade set like below

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY, optional = false)
@JoinColumn(name = "institution_id", nullable = false)
private Institution institution;