avoid peerDependencies WARNING

https://github.com/koajs/session/pull/218/files#r1060445443

And make both save() and regenerate() compatible with koa-passport

closes koajs#74

BREAKING CHANGE: drop Node.js < 18.19.0 support

[skip ci]

## [7.0.0](koajs/session@v6.4.0...v7.0.0) (2025-01-19)

### ⚠ BREAKING CHANGES

* drop Node.js < 18.19.0 support

### Features

* support cjs and esm both by tshy ([koajs#228](koajs#228)) ([575864c](koajs@575864c))

[skip ci]

## [7.0.1](koajs/session@v7.0.0...v7.0.1) (2025-01-19)

### Bug Fixes

* remove unused dependencies ([koajs#229](koajs#229)) ([3421008](koajs@3421008))

[skip ci]

## [7.0.2](koajs/session@v7.0.1...v7.0.2) (2025-01-19)

### Bug Fixes

* make sure options instance is not mutated ([koajs#230](koajs#230)) ([c45bf8b](koajs@c45bf8b))

Providing `nul` as `sameSite` will lead to errors.

Zod requires sameSite to be a string, so the description in the
documentation was inaccurate and has been corrected.

```
ZodError: [
  {
    "code": "invalid_type",
    "expected": "string",
    "received": "null",
    "path": [
      "sameSite"
    ],
    "message": "Expected string, received null"
  }
]
```

## Checklist

- [✅] I have ensured my pull request is not behind the main or master
branch of the original repository.
- [✅] I have rebased all commits where necessary so that reviewing this
pull request can be done without having to merge it first.
- [✅] I have written a commit message that passes commitlint linting.
- [✅] I have ensured that my code changes pass linting tests.
- [✅] I have ensured that my code changes pass unit tests.
- [✅] I have described my pull request and the reasons for code changes
along with context if necessary.