support dict as a parameter value on _build_params_header

[AvitalFineRedis]

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[sonarqubecloud]

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0.0% Duplication

[codecov]

Codecov Report

Merging #141 (5bbb6c3) into master (bb300e1) will decrease coverage by 0.56%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #141      +/-   ##
==========================================
- Coverage   85.46%   84.90%   -0.57%     
==========================================
  Files           8        8              
  Lines         523      530       +7     
==========================================
+ Hits          447      450       +3     
- Misses         76       80       +4     

Impacted Files	Coverage Δ
redisgraph/graph.py	85.43% <66.66%> (-2.07%)	⬇️

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[skieffer]

I think we need a recursive procedure, so that dictionaries occurring within a parameter value are also rendered without quotation marks around keys.

For example, we want this to work:

graph.query("""
    UNWIND $props as prop
    CREATE (c:Cat)
    SET c = prop
""", {
    'props': [
        {'age': 2, 'color': 'orange'},
        {'age': 7, 'color': 'gray'},
    ]
})

Therefore I'm proposing this pull request.

I put the stringifying function in the util module instead of the Graph class:

• so that it would be easier to write unit tests for it. (No need to instantiate a Graph,
  no need for a redis connection.)
• since it would have been a static method anyway, in the Graph class.