Prevent cyclic block updates

[nbenn]

This is intended to fix #159.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5d2cfcd) 79.40% compared to head (3ec14bd) 82.53%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #161      +/-   ##
==========================================
+ Coverage   79.40%   82.53%   +3.13%     
==========================================
  Files          16       16              
  Lines        1704     1701       -3     
==========================================
+ Hits         1353     1404      +51     
+ Misses        351      297      -54     

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[nbenn]

@DivadNojnarg how does this look to you? I believe this removes some of the unneeded executions of our update routines. At least it solves the cyclic updates for me.

At the time when we added

https://github.com/blockr-org/blockr/blob/1c5c1c87e9d67323ddf383d612102c84486b90b7/R/server.R#L120-L127

I was under the impression that this would not incur a dependency on blk but now it seems to me that it does, which would be unwanted.

As part of this PR I would also address #162.

[nbenn]

Closed in favor of #146.