[BUG] AppDataVariableService evaluator does not handle string values correctly

[jfmcquade]

As highlighted in #2107, the evaluator AppDataVariableService introduced in #2040 does not handle string values correctly. See tests added to src/app/shared/services/data/app-data-variable.service.spec.ts

Compare to appStringEvaluator.evaluate() method found in packages/shared/src/models/appStringEvaluator/appStringEvaluator.ts, which explicitly adds string delimiters.

[chrismclarke]

Just to copy from previous PR thread/add clarity

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Ah, yeah I see the challenge here - comparing the two cases:

1. hello @field.name
2. @field.name.startsWith("A")

In case (1) we want the string to just replace and return hello my_name
In case (2) we want the string to replace wrapped as a string "my_name".startsWith("A")

Currently we focus on supporting case (1). The parser attempts to evaluate, but reads hello and my_name as variables which are not defined, and has a fallback in case of such errors to just return the full expression as-is (as text)

I think the best way to also support case (2) would be to internally store a mapping of replaced strings when evaluating, which can then be used in follow-ups. E.g. for both cases above the mapping would simply be variables

{my_name: "my_name"}

Then when it comes to evaluation, case 1 will still just return as text (failing to recognise hello as a variable), but case 2 should be able to parse my_name.startsWith("A"), substituting the my_name variable for "my_name" string

I'll try make these changes in a follow-up PR as not so much targetted on the issue at hand