Allow index naming on JoinTable

[M-TGH]

Feature Description

Allowing to specify index names when creating a JoinTable.

The Problem

I'm personally looking to pick up an existing database with TypeORM and am trying to do so with minimal changes, unfortunately I can't count on index names being made with a single strategy for this. So a NamingStrategy might not be sufficient.

The Solution

Adding inputs for index names onto JoinTable, e.g.;

@JoinTable({
    indices: {
        ownerName: "index_user_id",
        inverseName: "index_role_id",
    },
})

Considered Alternatives

I considered fully adding indices here akin to JoinColumns being specified, however that complicates the work needed by a lot so for the meantime I opted for this. There may be other alternatives I haven't considered yet since I'm not too experienced with the code base at the moment.

Relevant Database Driver(s)

I don't think, no matter what changes get requested, this will need adjustments in database drivers.

DB Type	Relevant
aurora-data-api	no
aurora-data-api-pg	no
better-sqlite3	no
cockroachdb	no
cordova	no
expo	no
mongodb	no
mysql	no
nativescript	no
oracle	no
postgres	no
react-native	no
sap	no
sqlite	no
sqlite-abstract	no
sqljs	no
sqlserver	no

Are you willing to resolve this issue by submitting a Pull Request?

• ✅ Yes, I have the time, and I know how to start.
• ✖️ Yes, I have the time, but I don't know how to start. I would need guidance.
• ✖️ No, I don’t have the time, but I can support (using donations) development.
• ✖️ No, I don’t have the time and I’m okay to wait for the community / maintainers to resolve this issue.

I already have a commit ready for the changes as suggested in this issue, I'm opening the issue for a # to create the tests under and for early feedback on the idea. If need be and if so requested I should be able to make the alternative as mentioned as well (adding full index options), although would appreciate some pointers on execution of that.

[trylovetom]

Sounds great, maybe we can adding inputs for index names onto JoinTable, e.g.;

@JoinTable({
  name: 'paymentTransactions',
  joinColumn: {
    name: 'paymentId',
    foreignKeyConstraintName: 'payment',
    referencedColumnName: 'id',
    index: 'paymentIdx'
  },
  inverseJoinColumn: {
    name: 'transactionId',
    foreignKeyConstraintName: 'transaction',
    referencedColumnName: 'id',
    index: 'transactionIdx'
  }
})

[J4YF7O]

Hi, is a PR planned? What are the nexts steps on this subject? I wanted to migrate from V2.30 to V3.11, and given the change of strategy, we should pass / wait by this feature, to have zero downtime on our saas.

I really like the idea of @trylovetom :)

[hastom]

@JoinColumn needs this as well