clients: Add some tests for the catalyst client

[victorges]

Mainly to make sure that the rate limit logic is working.

[codecov]

Codecov Report

Merging #94 (ba21c02) into main (a5c91d2) will increase coverage by 38.64734%.
The diff coverage is 100.00000%.

@@               Coverage Diff               @@
##           main         #94          +/-   ##
===============================================
+ Coverage      0   38.64734%   +38.64734%     
===============================================
  Files         0           3           +3     
  Lines         0         207         +207     
===============================================
+ Hits          0          80          +80     
- Misses        0         119         +119     
- Partials      0           8           +8     

Impacted Files	Coverage Δ
clients/catalyst.go	94.82759% <100.00000%> (ø)
clients/base.go	32.46753% <0.00000%> (ø)
clients/ipfs.go	0.00000% <0.00000%> (ø)

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Impacted Files	Coverage Δ
clients/catalyst.go	94.82759% <100.00000%> (ø)
clients/base.go	32.46753% <0.00000%> (ø)
clients/ipfs.go	0.00000% <0.00000%> (ø)