## Why make this change?

- Closes #1632
- it's an unintended side effect of an optimisation pathway was added to
the deserializer in #1402.
Previously, deserializing the JSON config and replacing environment
variables were done as two separate parses of the config JSON blob.
First the JSON would be read from disk and then we'd create a JSON
reader that would walk all the tokens in the file, we'd check the token
to see if it matched the regex for an environment variable, we'd replace
it and then return the updated JSON string. Next this would be given to
the deserializer and it would be turned into the .NET object that we
would use throughout the engine. This meant that we'd end up walking the
AST for the JSON twice.
- With #1402, when we are doing deserialization we would also do the
environment variable replacement, meaning that we'd only walk the JSON
AST once, thus improving performance.
- There is a downside to this - the CLI doesn't need to do environment
variable replacements (since we don't need to actually connect to the DB
or anything, except for start, but that doesn't write out an updated
config).

## What is this change?

- Introduces a flag replaceEnvVar to determine whether to do the
environment variable replacement in the JsonConverters when being used
from the CLI commands. For `start` command this will be `true`, for all
other commands this is `false`.
- To minimize changes, default value of this argument was kept false.
All occurrences of callers requiring this flag were modified and set to
`true` in case of `start` or running the engine.
- For Enums, always replace the environment variable with its value for
appropriate deserialization into an Enum value.

## How was this tested?

- [X] Integration Tests - Modified the End2EndTests, to test the
commands `add`, `update` dont replace the environment variables, but
`start` replaces it.
- [X] Unit Tests - Modified the `CheckConfigEnvParsingTest` to test when
replaceEnvVar is `false` we dont replace them. The `true` scenario was
already being tested. Also modified the `database-type` property to be
an env variable for testing enums are always replaced with values.

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Co-authored-by: Sean Leonard <[email protected]>