Improve server call docs and increase code coverage

[marcoferrer]

No description provided.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (develop@7097cbb). Click here to learn what that means.
The diff coverage is 62.96%.

@@            Coverage Diff             @@
##             develop      #41   +/-   ##
==========================================
  Coverage           ?   85.77%           
  Complexity         ?       10           
==========================================
  Files              ?       12           
  Lines              ?      239           
  Branches           ?       27           
==========================================
  Hits               ?      205           
  Misses             ?       24           
  Partials           ?       10

Impacted Files	Coverage Δ	Complexity Δ
...oferrer/krotoplus/coroutines/GrpcContextElement.kt	100% <ø> (ø)	4 <0> (?)
...rrer/krotoplus/coroutines/client/ClientChannels.kt	100% <ø> (ø)	0 <0> (?)
...errer/krotoplus/coroutines/CoroutineCallOptions.kt	100% <ø> (ø)	0 <0> (?)
...ferrer/krotoplus/coroutines/server/ServiceScope.kt	0% <0%> (ø)	0 <0> (?)
...oferrer/krotoplus/coroutines/server/ServerCalls.kt	84.48% <45.45%> (ø)	0 <0> (?)
.../marcoferrer/krotoplus/coroutines/call/CallExts.kt	71.64% <80%> (ø)	0 <0> (?)

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