Fix: Ensure Content-Type is set based on header value if not explicitly set

[KyrillosNageh]

Fixes #1697

This PR ensures that the Content-Type is set based on the header value if it is not explicitly set by the user.

• Modified the prepareRequestSpecs method to check if contentType is still ContentType.ANY.
• If ContentType is not explicitly set by the user, it now retrieves the Content-Type from sessionHeaders and applies it directly to the RequestSpecBuilder.
• This change ensures that the request uses the exact Content-Type provided in the headers, preventing encoding and serialization issues.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 52.57%. Comparing base (5652a7c) to head (93c6e96). Report is 1 commits behind head on main.

Files	Patch %	Lines
src/main/java/com/shaft/api/RestActions.java	33.33%	2 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1704 +/- ## ============================================ - Coverage 52.67% 52.57% -0.11% Complexity 1268 1268 ============================================ Files 112 112 Lines 9993 9998 +5 Branches 962 964 +2 ============================================ - Hits 5264 5256 -8 - Misses 4123 4138 +15 + Partials 606 604 -2 ```

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