How can I implement a mutual friendship relationship in a database?

Question

I am designing a database schema for a social network
and need to implement mutual friend relationships between users in a database.

But what is the best way to represent such a relationship in the database? Is it even possible?

As an example, I will take a sample from Prisma.
The follower relationship is implemented there like this, although it doesn't guarantee reciprocity:

CREATE TABLE "User" (
    id integer DEFAULT nextval('"User_id_seq"'::regclass) PRIMARY KEY,
    name text
);
CREATE TABLE "_UserFollows" (
    "A" integer NOT NULL REFERENCES "User"(id) ON DELETE CASCADE ON UPDATE CASCADE,
    "B" integer NOT NULL REFERENCES "User"(id) ON DELETE CASCADE ON UPDATE CASCADE
);

model User {
  id         Int       @id @default(autoincrement())
  name       String?
  followedBy Follows[] @relation("following")
  following  Follows[] @relation("follower")
}

model Follows {
  follower    User @relation("follower", fields: [followerId], references: [id])
  followerId  Int
  following   User @relation("following", fields: [followingId], references: [id])
  followingId Int

  @@id([followerId, followingId])
}

How can I ensure data integrity and atomicity of changes? Additionally, how can I make sure that when a relationship is deleted from one side, the relationship from the other side is also deleted?