Migrate tink-server to cobra and viper

[gianarb]

This PR refactors how tink-server starts.
It uses Cobra and Viper same as tink-cli and tink-worker.

Right now it tries to keep compatibility with the old way of doing
things.

TODO:

• run this version in sandbox without any change. it should work like before
• Unit test (project aborted, I don't know how to mock env var!)

Signed-off-by: Gianluca Arbezzano gianarb92@gmail.com

[gianarb]

@displague you did a similar job for the other binaries. Can you have a look and tell me if it makes sense? I know you don't like to keep "useless retro-compatibility" but the code will get removed soon trust me!! 😇

Thanks

[codecov]

Codecov Report

Merging #431 (06ce919) into master (a7e947e) will increase coverage by 0.08%.
The diff coverage is 23.61%.

@@            Coverage Diff             @@
##           master     #431      +/-   ##
==========================================
+ Coverage   34.73%   34.82%   +0.08%     
==========================================
  Files          47       47              
  Lines        2893     2886       -7     
==========================================
  Hits         1005     1005              
+ Misses       1796     1789       -7     
  Partials       92       92              

Impacted Files	Coverage Δ
grpc-server/events.go	0.00% <0.00%> (ø)
grpc-server/grpc_server.go	0.00% <0.00%> (ø)
grpc-server/hardware.go	1.55% <0.00%> (ø)
http-server/http_server.go	0.00% <0.00%> (ø)
grpc-server/workflow.go	28.80% <36.84%> (ø)
grpc-server/template.go	36.53% <47.05%> (ø)
grpc-server/tinkerbell.go	92.12% <66.66%> (ø)

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[gianarb]

@detiber I know you have this PR #266 in the fight but let's hold (it is pretty stale already) it until we figure out #432

[gianarb]

$ go run cmd/tink-server/main.go --help
Usage:
  tink-server [flags]

Flags:
      --cert-dir string
      --facility string            This is temporary. It will be removed (default "deprecated")
      --grpc-authority string      The address used to expose the gRPC server (default ":42113")
  -h, --help                       help for tink-server
      --http-authority string      The address used to expose the HTTP server (default ":42114")
      --only-migration             When enabled the server applies the migration to postgres database and it exits
      --postgres-database string   The Postgres database name (default "tinkerbell")
      --postgres-password string   The Postgres database password (default "tinkerbell")
      --postgres-sslmode string    Enable or disable SSL mode in postgres (default "disable")
      --postgres-user string       The Postgres database username (default "tinkerbell")
      --tls-cert string