Update integration tests to use host.testcontainers.internal

[minwoox]

Motivation
While I was running the integration test, I found out that host.docker.internal doesn't work correctly on Linux. (It worked on Mac and Windows.) host.docker.internal is used for the container to access the host but the DNS resolution was keeping failing. While I was debugging on it, I also found out that the Testcontainers provides host.testcontainers.internal for the same purpose and there's no reason not to use it. https://java.testcontainers.org/features/networking/

Modification

• Use host.testcontainers.internal instead of host.docker.internal

Result

• The integration tests now run successfully on Linux.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.16%. Comparing base (95048ae) to head (40ddc19).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #303   +/-   ##
=========================================
  Coverage     86.16%   86.16%           
  Complexity      361      361           
=========================================
  Files            42       42           
  Lines          1178     1178           
  Branches         97       97           
=========================================
  Hits           1015     1015           
  Misses          116      116           
  Partials         47       47           

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