Add grpc interceptors

[ribice]

Closes #240

Sample error logged to Sentry:

Possible improvements / todos:

• Create docs in sentry and sentry-docs
• The options is a simple struct (as in other integrations). Could implement Functional Options Pattern for these.
• More tests and examples?

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.85799% with 7 lines in your changes missing coverage. Please review.

Project coverage is 84.32%. Comparing base (6b014ea) to head (6b3eefb). Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
grpc/server.go	94.30%	5 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #938      +/-   ##
==========================================
+ Coverage   84.00%   84.32%   +0.31%     
==========================================
  Files          50       52       +2     
  Lines        5171     5340     +169     
==========================================
+ Hits         4344     4503     +159     
- Misses        673      680       +7     
- Partials      154      157       +3     

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