test: add api and doc http test

[jun0315]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

add http's api and doc IT.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

#983

[shuiyisong]

iirc we already have a DummyInstance, could we reuse that?

[waynexia]

Not sure if integration-test is a better place for this kind of URL test. cc @sunng87

[codecov]

Codecov Report

Merging #998 (af0b252) into develop (8491f65) will increase coverage by 0.10%.
The diff coverage is n/a.

❗ Current head af0b252 differs from pull request most recent head 16094bf. Consider uploading reports for the commit 16094bf to get more accurate results

@@             Coverage Diff             @@
##           develop     #998      +/-   ##
===========================================
+ Coverage    86.05%   86.16%   +0.10%     
===========================================
  Files          431      432       +1     
  Lines        61600    62494     +894     
===========================================
+ Hits         53008    53845     +837     
- Misses        8592     8649      +57     

Flag	Coverage Δ
rust	86.16% <ø> (+0.10%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/object-store/src/test_util.rs	0.00% <0.00%> (-100.00%)	⬇️
src/storage/src/compaction/task.rs	7.47% <0.00%> (-59.20%)	⬇️
src/datanode/src/instance.rs	41.56% <0.00%> (-14.91%)	⬇️
src/storage/src/compaction/picker.rs	26.53% <0.00%> (-11.71%)	⬇️
tests-integration/src/test_util.rs	79.47% <0.00%> (-9.33%)	⬇️
src/storage/src/read.rs	89.88% <0.00%> (-2.97%)	⬇️
src/storage/src/test_util/read_util.rs	92.78% <0.00%> (-1.58%)	⬇️
src/query/src/optimizer.rs	93.11% <0.00%> (-0.41%)	⬇️
src/storage/src/manifest/test_utils.rs	100.00% <0.00%> (ø)
src/storage/src/compaction/writer.rs	100.00% <0.00%> (ø)
... and 23 more

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[sunng87]

@waynexia Since these test only covers http server I think it's ok to keep it here

[fengys1996]

LGTM

[shuiyisong]

LGTM