bau/code refactor r2 - v1.4.0

[bhaskarkishore]

High level changelog:

• Switched to AWS SDK
• Updated dependency versions
• Switched to Jemallocator instead of Std allocator. Unused memory will be returned to the OS quickly.
• Added metric for tracking mime type.
• Added metric for tracking api key usage
• Refactored DB and HTTP modules for supporting multiple providers.
• New API Key configuration has been introduced. The old style config is deprecated.

closes #76, closes #70, closes #74, closes #73, closes #49, partially closes #45

[codecov-commenter]

Codecov Report

Merging #75 (81f7e5f) into main (678f860) will increase coverage by 24.66%.
The diff coverage is 35.18%.

@@            Coverage Diff            @@
##           main      #75       +/-   ##
=========================================
+ Coverage      0   24.66%   +24.66%     
=========================================
  Files         0       23       +23     
  Lines         0     1488     +1488     
  Branches      0      312      +312     
=========================================
+ Hits          0      367      +367     
- Misses        0      980      +980     
- Partials      0      141      +141     

Impacted Files	Coverage Δ
src/aws/mod.rs	0.00% <0.00%> (ø)
src/config.rs	0.00% <0.00%> (ø)
src/db/postgres.rs	0.00% <0.00%> (ø)
src/metrics.rs	0.00% <0.00%> (ø)
src/moderation.rs	0.00% <0.00%> (ø)
src/rpc/error.rs	0.00% <0.00%> (ø)
src/rpc/mod.rs	0.00% <0.00%> (ø)
src/rpc/requests.rs	0.00% <0.00%> (ø)
src/rpc/responses.rs	0.00% <0.00%> (ø)
src/utils.rs	35.71% <ø> (ø)
... and 26 more