feat: enable POST requests batching with dl.

[laststylebender14]

Summary:
docs: tailcallhq/tailcallhq.github.io#559

Issue Reference(s):
Fixes #... (Replace "..." with the issue number)

Build & Testing:

• I ran cargo test successfully.
• I have run ./lint.sh --mode=fix to fix all linting issues raised by ./lint.sh --mode=check.

Checklist:

• I have added relevant unit & integration tests.
• I have updated the documentation accordingly.
• I have performed a self-review of my code.
• PR follows the naming convention of <type>(<optional scope>): <title>

[codecov]

Codecov Report

Attention: Patch coverage is 94.58204% with 35 lines in your changes missing coverage. Please review.

Project coverage is 86.78%. Comparing base (626b142) to head (b8ce74a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/core/ir/request.rs	62.50%	9 Missing ⚠️
src/core/json/borrow.rs	0.00%	6 Missing ⚠️
src/core/json/serde.rs	0.00%	6 Missing ⚠️
src/core/http/data_loader_request.rs	80.00%	4 Missing ⚠️
src/core/json/graphql.rs	50.00%	3 Missing ⚠️
src/core/blueprint/operators/http.rs	96.77%	2 Missing ⚠️
src/core/http/data_loader.rs	96.66%	2 Missing ⚠️
src/core/http/request_template.rs	97.84%	2 Missing ⚠️
src/core/ir/eval_http.rs	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3140      +/-   ##
==========================================
+ Coverage   86.66%   86.78%   +0.12%     
==========================================
  Files         278      281       +3     
  Lines       27924    28435     +511     
==========================================
+ Hits        24201    24678     +477     
- Misses       3723     3757      +34     

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[github-actions]

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