[Python] Code generator doesn't preserve original case for variables

[ShemTovYosef]

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\.
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Description of the PR

Solves this issue: #12505
Provides support in codegen for Python to preserve original names for variables

Usage example with maven plugin:

<plugin>
                <groupId>io.swagger</groupId>
                <artifactId>swagger-codegen-maven-plugin</artifactId>
                <version>2.4.41</version>
                <executions>
                    <execution>
                        <id>python-swagger-client</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${basedir}/target/resources/services.yaml</inputSpec>
                            <output>${basedir}/target/generated_sources</output>
                            <templateDirectory>${basedir}/templates</templateDirectory>
                            <generateApiTests>false</generateApiTests>
                            <generateModelTests>false</generateModelTests>
                            <language>python</language>
                            <additionalProperties>
                                <property>case=original</property>
                            </additionalProperties>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

[ShemTovYosef]

Hi @frantuma can you review please?

[ShemTovYosef]

Hi @Alexizx00789999
Thank you for approving but it still requires someone with write access, do you know who can help ?

[ShemTovYosef]

Hi @frantuma @HugoMario can you merge it please?