refactor: crud insert many

[flower-of-the-bridges]

Pull Request Type

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

Description

This PR improves the performances of the POST /bulk operation, by avoiding to create multiple copies of the batch that has to be inserted.

PR Checklist

• The commit message follows our guidelines included in the CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Does this PR introduce a breaking change?

• Yes
• No

Other information

A k6 test has been added on the bench/scripts folder, named bulk-test.js. In this test, 10k records are inserted in batches into the records folder, using up to 80 concurrent requests.

This is the outcome for the version from the current branch:

✓ checks.........................: 100.00% ✓ 14       ✗ 0   
data_received..................: 4.9 MB  18 kB/s
data_sent......................: 65 MB   235 kB/s
http_req_blocked...............: avg=180.18ms min=6.55µs   med=141.76ms max=499.23ms p(90)=416.23ms p(95)=449.42ms
http_req_connecting............: avg=179.51ms min=0s       med=141.63ms max=498.16ms p(90)=414.17ms p(95)=447.17ms
http_req_duration..............: avg=2.29s    min=19.39ms  med=1.96s    max=5.56s    p(90)=4.1s     p(95)=4.73s   
  { expected_response:true }...: avg=2.29s    min=19.39ms  med=1.96s    max=5.56s    p(90)=4.1s     p(95)=4.73s   
✓ { type:bulk }................: avg=2.46s    min=787.93ms med=2.2s     max=5.56s    p(90)=4.16s    p(95)=4.79s   
✓ http_req_failed................: 0.00%   ✓ 0        ✗ 14  
http_req_receiving.............: avg=220.31ms min=910.4µs  med=4.75ms   max=2s       p(90)=519.01ms p(95)=1.07s   
http_req_sending...............: avg=993.43ms min=42.51µs  med=701.65ms max=3.56s    p(90)=2.33s    p(95)=2.85s   
http_req_tls_handshaking.......: avg=0s       min=0s       med=0s       max=0s       p(90)=0s       p(95)=0s      
http_req_waiting...............: avg=1.08s    min=17.93ms  med=1.15s    max=1.62s    p(90)=1.46s    p(95)=1.52s   
http_reqs......................: 14      0.050999/s
iteration_duration.............: avg=47.84s   min=332.17µs med=34.37s   max=3m3s     p(90)=1m39s    p(95)=2m6s    
iterations.....................: 13      0.047356/s
vus............................: 0       min=0      max=50
vus_max........................: 50      min=50     max=50