Aligned MongooseModuleOptions with MongooseModuleAsyncOptions

[BorntraegerMarc]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[X] Other... Please describe: Refactoring with API changes

What is the current behavior?

Options aren't really aligned and don't make sense.

Issue Number: #244

What is the new behavior?

See linked issue for description.

Does this PR introduce a breaking change?

[X] Yes
[ ] No

Applications will need to move from this: MongooseCoreModule.forRoot('mongooseUri', {}) to this -> MongooseCoreModule.forRoot({uri: 'mongooseUri'})

Should be an easy migration

Other information

I'll create a squash & merge so we have 1 clean commit msg

[BorntraegerMarc]

Docs have been added / updated (for bug fixes / features)

Where should I adapt the docs?

Also I was wondering if we should create a v7 branch or a next branch for changes that will be released in the next major version?

[dantehemerson]

This is a breaking change, could we support both cases in this module and add a deprecation warning?

[BorntraegerMarc]

We could, technically. Yes.

Although I'm more in favour to add a single breaking change & document it properly. Adaptation for consumers for this breaking change should be simple enough.

But either way: I'm not really willing to invest more time into this PR and make further changes, since it seems like to me that this PR will not get merged (open for more than 1 year)...