feat: add capability for insert multiple rows in single query

[samarpanB]

Signed-off-by: Samarpan Bhattacharya [email protected]

Adds new createAll method to support insert multiple rows in single query in memory connector Enables multiInsertSupport in memory connector Adds capability to createAll in dao.js for models to do multiple insert in one query via the supported connectors

Fixes https://github.com/loopbackio/loopback-connector/issues/227 See also https://github.com/loopbackio/loopback-next/issues/3357

Checklist

• [x] Sign off your commits with DCO (Developer Certificate of Origin)
• [x] npm test passes on your machine
• [x] New tests added or existing tests modified to cover all changes
• [x] Code conforms with the style guide
• [x] Commit messages are following our guidelines

[coveralls]

Pull Request Test Coverage Report for Build 3167967406

• 91 of 106 (85.85%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.09%) to 84.667%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/connectors/memory.js	11	13	84.62%
lib/dao.js	80	93	86.02%
<!--	Total:	91	106

Totals
Change from base Build 3155109076:	-0.09%
Covered Lines:	7250
Relevant Lines:	8255

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💛 - Coveralls

[samarpanB]

Added persistence hooks test cases as well. While adding those, I found some issues, fixed them as well. Please review @dhmlau @achrinza

[samarpanB]

loopback-connector release is needed before it can be merged. However, this can be reviewed until then.

[samarpanB]

Updated connector version after rebase.

[samarpanB]

@raymondfeng @achrinza @dhmlau Please review.

[samarpanB]

@dhmlau I replied to your comment. Can you please check if I need to change the behaviour ?

[dhmlau]

@samarpanB, thanks for your response. LGTM. Since I have the "go ahead" from @achrinza as well, I'll be merging this PR. Thanks!