Keep the libcurl header out of CcdbApi.h

[sawenzel]

Moves the libcurl dependency out of the public CcdbApi.h header and keeps it in the implementation where it belongs. This makes the header self-contained and allows ROOT to interpret it without requiring the curl headers.

[Barthelemy]

this is great, thanks !

[alibuild]

Error while checking build/O2/fullCI_slc9 for 10df9ff at 2026-09-01 15:33:

## sw/BUILD/QualityControl-latest/log
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:310:15: error: 'thread' is not a member of 'std'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:310:21: error: template argument 1 is invalid
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:310:21: error: template argument 2 is invalid
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:314:13: error: request for member 'emplace_back' in 'threads', which is of non-class type 'int'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:317:13: error: 'thread' is not a member of 'std'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:317:23: error: found ':' in nested-name-specifier, expected '::'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:317:21: error: 't' has not been declared
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:320:11: error: request for member 'clear' in 'threads', which is of non-class type 'int'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:321:1: error: expected primary-expression before '}' token
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:320:19: error: expected ')' before '}' token
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:321:1: error: expected primary-expression before '}' token
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:345:15: error: 'thread' is not a member of 'std'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:345:21: error: template argument 1 is invalid
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:345:21: error: template argument 2 is invalid
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:349:13: error: request for member 'emplace_back' in 'threads', which is of non-class type 'int'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:350:10: error: 'std::this_thread' has not been declared
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:353:13: error: 'thread' is not a member of 'std'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:353:23: error: found ':' in nested-name-specifier, expected '::'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:353:21: error: 't' has not been declared
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:356:11: error: request for member 'clear' in 'threads', which is of non-class type 'int'
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:357:1: error: expected primary-expression before '}' token
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:356:19: error: expected ')' before '}' token
/sw/SOURCES/QualityControl/v1.195.4/v1.195.4/Framework/test/testCcdbDatabase.cxx:357:1: error: expected primary-expression before '}' token
ninja: build stopped: cannot make progress due to previous errors.


## sw/BUILD/o2checkcode-latest/log
--
========== List of errors found ==========
++ GRERR=0
++ grep -v clang-diagnostic-error error-log.txt
++ grep ' error:'
grep: error-log.txt: binary file matches
++ GRERR=1
++ [[ 1 == 0 ]]
++ mkdir -p /sw/INSTALLROOT/c1801fbc3d91036955edb28fb01e6f8b24ec5b79/slc9_x86-64/o2checkcode/1.0-local497/etc/modulefiles
++ alibuild-generate-module
+ HAS_BIN=
+ HAS_LIB=
+ HAS_CMAKE=
+ HAS_ROOT=
+ '[' 0 '!=' 0 ']'
+ cat
+ printf 'if ![ is-loaded '\''BASE/1.0'\'' ] {\n module load BASE/1.0\n}'
+ echo 'BUILD_REQUIRES=CMake alibuild-recipe-tools defaults-release'
BUILD_REQUIRES=CMake alibuild-recipe-tools defaults-release
+ FULL_BUILD_REQUIRES='Python-modules-list MPFR bz2 json-c CMake Alice-GRID-Utils ninja-fortran pytorch_cpuinfo O2-customization defaults-release UUID ninja safe_int date FairCMakeModules double-conversion googlebenchmark alibuild-recipe-tools'
+ echo 'FULL_BUILD_REQUIRES=Python-modules-list MPFR bz2 json-c CMake Alice-GRID-Utils ninja-fortran pytorch_cpuinfo O2-customization defaults-release UUID ninja safe_int date FairCMakeModules double-conversion googlebenchmark alibuild-recipe-tools'
[0 more errors; see full log]

Full log here.