[cpp-restsdk] Fix handling of UUID types

[Peaches491]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: master, 3.1.x, 4.0.x. Default: master.
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Description of the PR

Fixes handling of UUID types, preventing the generation of std::shared_ptr<utility::string_t> members in models.

NOTE: This PR does not effect the petshop sample, as petshop.json does not make use of format: "uuid"

[Peaches491]

@Danielku15 I believe you're the required reviewer for this PR as well

[wing328]

@Peaches491 thanks for the PR. cc'ing the technical committee for review:

@ravinikam (2017/07) @stkrwork (2017/07) @fvarose (2017/11) @etherealjoy (2018/02) @MartinDelille (2018/03)

[wing328]

@Peaches491 thanks again for the PR. Should the isStringSchema check at line 301 already cover that (type: string)?

    public static boolean isStringSchema(Schema schema) {
        if (schema instanceof StringSchema || SchemaTypeUtil.STRING_TYPE.equals(schema.getType())) {
            return true;
        }
        return false;
    }

Ref: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java#L324-L329

[Peaches491]

I don't believe so, since adding this caused the generated code to be different. Specifically, string parameters with format: "uuid" were no longer used a std::shared_ptr<utilities::string_t> and instead just used the expected utilities::string_t

[wing328]

You're right. I did a test with latest master and got:

         int64_t petId,
-        boost::optional<utility::string_t> name,
+        boost::optional<std::shared_ptr<utility::string_t>> name,
         boost::optional<utility::string_t> status

[wing328]

@Peaches491 thanks for the PR, which has been merged into master.