Send project-specific User-Agent HTTP header

[jakob-keller]

Description of Change

Includes aiobotocore identifier and version in default User-Agent HTTP header.

Assumptions

Customizing the default User-Agent HTTP header is beneficial for this project and AWS, while not impacting users. See #853 for discussion.

Checklist for All Submissions

• I have added change info to CHANGES.rst
• If this is resolving an issue (needed so future developers can determine if change is still necessary and under what conditions) (can be provided via link to issue with these details):
  • Detailed description of issue
  • Alternative methods considered (if any)
  • How issue is being resolved
  • How issue can be reproduced
• If this is providing a new feature (can be provided via link to issue with these details): closes Feature Request: AioBotocore Specific User-Agent #853
  • Detailed description of new feature: Add method AioSession._set_user_agent_for_session() which is called in AioSession.__init__() and mimics the behaviour taken by aws-cli.
  • Why needed
  • Alternatives methods considered (if any): see Feature Request: AioBotocore Specific User-Agent #853 and aioboto user agent #870

Checklist when updating botocore and/or aiohttp versions

• I have read and followed CONTRIBUTING.rst
• I have updated test_patches.py where/if appropriate (also check if no changes necessary)
• I have ensured that the awscli/boto3 versions match the updated botocore version

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (743c26f) 86.25% compared to head (a63e037) 86.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1075      +/-   ##
==========================================
- Coverage   86.25%   86.23%   -0.03%     
==========================================
  Files          60       60              
  Lines        5858     5870      +12     
==========================================
+ Hits         5053     5062       +9     
- Misses        805      808       +3     

Flag	Coverage Δ
unittests	86.23% <100.00%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.