fix: add and use post endpoint for streaming

[NarekA]

Making a new PR that follows conventions to replace https://github.com/jina-ai/jina/pull/6091

Http streaming breaks when the input doc schema has fields which are not str, int, or float. This includes dicts, bools, and nested objects (See Issue 6090). In addition it caps the input size to 2000 characters (Much less when you factor in URL encoding)

This PR changes the get endpoints to post endpoints. Not sure if we want to keep the get endpoints for backwards compatibility.

Goals:

• resolves Issue 6090
• [x] check and update documentation. See guide and ask the team.

[codecov[bot]]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (2c3d7d3) 76.36% compared to head (f1f9a88) 76.17%. Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #6093 +/- ## ========================================== - Coverage 76.36% 76.17% -0.20% ========================================== Files 145 145 Lines 14007 14020 +13 ========================================== - Hits 10697 10680 -17 - Misses 3310 3340 +30 ``` | [Flag](https://app.codecov.io/gh/jina-ai/jina/pull/6093/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai) | Coverage Δ | | |---|---|---| | [jina](https://app.codecov.io/gh/jina-ai/jina/pull/6093/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai) | `76.17% <38.46%> (-0.20%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/jina-ai/jina/pull/6093?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai) | Coverage Δ | | |---|---|---| | [jina/\_\_init\_\_.py](https://app.codecov.io/gh/jina-ai/jina/pull/6093?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai#diff-amluYS9fX2luaXRfXy5weQ==) | `56.00% <100.00%> (ø)` | | | [jina/clients/base/helper.py](https://app.codecov.io/gh/jina-ai/jina/pull/6093?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai#diff-amluYS9jbGllbnRzL2Jhc2UvaGVscGVyLnB5) | `82.94% <100.00%> (-2.21%)` | :arrow_down: | | [jina/serve/runtimes/worker/http\_fastapi\_app.py](https://app.codecov.io/gh/jina-ai/jina/pull/6093?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai#diff-amluYS9zZXJ2ZS9ydW50aW1lcy93b3JrZXIvaHR0cF9mYXN0YXBpX2FwcC5weQ==) | `69.42% <61.53%> (-12.73%)` | :arrow_down: | | [...ve/runtimes/gateway/http\_fastapi\_app\_docarrayv2.py](https://app.codecov.io/gh/jina-ai/jina/pull/6093?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai#diff-amluYS9zZXJ2ZS9ydW50aW1lcy9nYXRld2F5L2h0dHBfZmFzdGFwaV9hcHBfZG9jYXJyYXl2Mi5weQ==) | `0.00% <0.00%> (ø)` | | ... and [10 files with indirect coverage changes](https://app.codecov.io/gh/jina-ai/jina/pull/6093/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jina-ai)

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[NarekA]

@JoanFM I addressed the your comments. Please let me know If there's anything else I can do.

[JoanFM]

Hey @NarekA ,

Thanks for the contrubution, could yiu add a note in the documentation https://docs.jina.ai/concepts/serving/executor/add-endpoints/#streaming-endpoints making explicit note that SSE can only be used with flat schemas?

[JoanFM]

@JoanFM I addressed the your comments. Please let me know If there's anything else I can do.

It looks good to me, but there seems to be a failing test

[NarekA]

@JoanFM I am trying to fix the tests, but I'm having issues recreating CI tests locally, or even seeing what the failure is in CI. (Will go back and read the docs to see what I missed)

[JoanFM]

Thanks @NarekA for the great contribution