fix: url usages

[Stun3R]

Types of changes

• [x] Bug fix (a non-breaking change which fixes an issue)
• [ ] New feature (a non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Other changes (could be a refactor, documentation change ect...)

Description

• It fixes the way the baseUrl is built. We get rid of new URL() to use joinURL from unjs/ufo. Fixes: #145
• It adds missing prefix to the method getProviderAuthenticationUrl. Fixes #140

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes (if not applicable, please state why)

[codecov[bot]]

Codecov Report

Merging #177 (da42bbb) into develop (3e0fa76) will increase coverage by 0.24%. Report is 37 commits behind head on develop. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #177      +/-   ##
===========================================
+ Coverage    96.11%   96.36%   +0.24%     
===========================================
  Files            3        3              
  Lines          103      110       +7     
  Branches        19       19              
===========================================
+ Hits            99      106       +7     
  Misses           3        3              
  Partials         1        1              

Files Changed	Coverage Δ
src/lib/strapi.ts	96.22% <100.00%> (+0.26%)	:arrow_up: