[chore] Minor fixes for server compatibility

[zmbush]

Also, fix the uniqueness constraint on notes

[todo]

Server needs Postgres 9.5 to support ON CONFLICT DO NOTHING

In the meantime, we will just ignore the result from the following execute.

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noted/db/src/models.rs

Lines 254 to 259 in 0787ff0

	// TODO: Server needs Postgres 9.5 to support ON CONFLICT DO NOTHING
	// BODY: In the meantime, we will just ignore the result from the following execute.
	let _ = diesel::insert_into(tags)
	.values(&set_tags.iter().map(|t| tag.eq(t)).collect::<Vec<_>>())
	// .on_conflict_do_nothing()
	.execute(db);

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This comment was generated by todo based on a TODO comment in 0787ff0 in #65. cc @zmbush.

[codecov]

Codecov Report

Merging #65 into master will increase coverage by 3.17%.
The diff coverage is 95.23%.

@@            Coverage Diff             @@
##           master      #65      +/-   ##
==========================================
+ Coverage   41.37%   44.55%   +3.17%     
==========================================
  Files          23       23              
  Lines         899      918      +19     
  Branches       22       22              
==========================================
+ Hits          372      409      +37     
+ Misses        527      509      -18

Impacted Files	Coverage Δ
db/src/models.rs	87.91% <95.23%> (+12.45%)	⬆️

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