feat: add deprecation warnings to 0.2 branch in preparation for 0.3

[jbr]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 55.76923% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 48.76%. Comparing base (6f328bd) to head (ee32862).

Files	Patch %	Lines
http/src/upgrade.rs	0.00%	4 Missing ⚠️
proxy/src/lib.rs	0.00%	4 Missing ⚠️
static/src/static_conn_ext.rs	0.00%	3 Missing ⚠️
aws-lambda-example/src/main.rs	0.00%	2 Missing ⚠️
caching-headers/src/cache_control.rs	0.00%	2 Missing ⚠️
client/src/conn.rs	50.00%	2 Missing ⚠️
sse/src/lib.rs	0.00%	2 Missing ⚠️
trillium/src/conn.rs	60.00%	2 Missing ⚠️
api/src/api_conn_ext.rs	66.66%	1 Missing ⚠️
redirect/src/lib.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #624      +/-   ##
==========================================
- Coverage   48.77%   48.76%   -0.02%     
==========================================
  Files         182      182              
  Lines        7233     7241       +8     
==========================================
+ Hits         3528     3531       +3     
- Misses       3705     3710       +5     

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