feat(mikro-orm): provide the ability to avoid an explicit transaction

[derevnjuk]

Information

Type	Breaking change
Feature	No

---

In some cases, you might need to avoid an explicit transaction, but preserve an async context to prevent the usage of the global identity map. For example, starting with v3.4, the MongoDB driver supports transactions. Yet, you have to use a replica set, otherwise, the driver will raise an exception.

Usage example

To prevent @Transactional() use of an explicit transaction, you just need to set the disabled field to true:

@Post("/")
@Transactional({disabled: true})
create(@BodyParams() user: User): Promise<User> {
  return this.usersService.create(user);
}

You can also set the flushing strategy for the transaction by setting the flushMode:

@Post("/")
@Transactional({flushMode: FlushMode.AUTO})
create(@BodyParams() user: User): Promise<User> {
  return this.usersService.create(user);
}

Todos

• Tests
• Coverage
• Example
• Documentation

closes #1996

[Romakita]

Perfect :) @derevnjuk

You can click on merge button when you are ready ;)

See you :D

[coveralls]

Pull Request Test Coverage Report for Build 2714197662

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.769%

---

Totals
Change from base Build 2710793819:	0.0%
Covered Lines:	3584
Relevant Lines:	3725

---

💛 - Coveralls

[Romakita]

🎉 This PR is included in version 6.118.0 🎉

The release is available on:

• v6.118.0
• GitHub release

Your semantic-release bot 📦🚀

[Romakita]

🎉 This PR is included in version 7.0.0-beta.13 🎉

The release is available on:

• v7.0.0-beta.13
• GitHub release

Your semantic-release bot 📦🚀

[coveralls]

Pull Request Test Coverage Report for Build 2713456200

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.769%

---

Totals
Change from base Build 2710793819:	0.0%
Covered Lines:	3584
Relevant Lines:	3725

---

💛 - Coveralls