Export cpg as json via Neo4j OGM

[peckto]

This PR adds the functionality to export the cpg as json.
The serialization is done via the Neo4j OGM.
Basically the same as when importing to Neo4j Database, just without Database.
So the json export will suffer from known problems, like recursion and bigInt.

Json format might be useful for machine learning or other data science projects.

Proposed json format:

{
"nodes": [],
"edges": []
}

Example json file:
cpg.txt

• compare json export with data from Neo4j Database import
• add test case
• support pre-save hooks

Closes #247 #776 #935

[peckto]

The current implementation does not create any Neo4j Session object, which allows the json export to be used without a connection to the database server, which is of course desirable.
This has unfortunately the side effect, that pre-save hooks are not executed, because they are configured in the session.
I have currently three ideas how this could be fixed:
a) create some dummy session, without actual database connection
b) configure pre-save hooks without session
c) do not use the OGM pre-save hook functionality and instead do this by our self

Update: I now implemented option (c).

[KuechA]

Related issues: #247 #776 #935 . We may want to enable customizing the output format somehow.

[peckto]

We may want to enable customizing the output format somehow

Good point! I created a separate function to export in the proposed json format (exportSimpleJson) .
In future, here one could step in to support other formats.

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

65.2% Coverage
0.0% Duplication

Catch issues before they fail your Quality Gate with our IDE extension SonarLint

[konradweiss]

• Make a pass PrepareForNeo4jSerializationPass
• Turn it on as a default pass for the Neo4j module.

[CLAassistant]

All committers have signed the CLA.

[konradweiss]

I would change some names and add more explicit explanations in the form of function comments. Just to make it a bit more maintainable. I did also think whether or not it would be good to extract the export to json functionality into its own class to not overload the Application.kt but for now its fine so that is optional.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

85.3% Coverage
0.0% Duplication