feat: add support for new endpoint of Protocol 14.

[overcat]

No description provided.

[codecov]

Codecov Report

Merging #373 into dev-protocol-14 will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@               Coverage Diff                @@
##           dev-protocol-14     #373   +/-   ##
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  Coverage            98.98%   98.99%           
================================================
  Files                  125      127    +2     
  Lines                 7501     7566   +65     
================================================
+ Hits                  7425     7490   +65     
  Misses                  76       76           

Flag	Coverage Δ
#unittests	98.99% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
stellar_sdk/call_builder/__init__.py	100.00% <100.00%> (ø)
stellar_sdk/call_builder/accounts_call_builder.py	100.00% <100.00%> (ø)
...dk/call_builder/claimable_balances_call_builder.py	100.00% <100.00%> (ø)
stellar_sdk/call_builder/offers_call_builder.py	90.62% <100.00%> (+0.96%)	⬆️
stellar_sdk/server.py	98.13% <100.00%> (+0.02%)	⬆️
tests/call_builder/test_accounts_call_builder.py	100.00% <100.00%> (ø)
...ll_builder/test_claimable_balances_call_builder.py	100.00% <100.00%> (ø)
tests/call_builder/test_offers_call_builder.py	100.00% <100.00%> (ø)
tests/test_server.py	100.00% <100.00%> (ø)
... and 1 more