[$40] Setting StartDate for default and explicitly added phases

[RishiRajSahu]

Currently, we don't set start date of a phase during creation. We need to persist start date as well during creation of phase whether its default phase for a project or its a newly added phase.

fyi @vikasrohit @rmjmccormick @acshields

Requirements:

1. Update POST /v4/projects endpoint to set the current date as phase startDate and set the endDate as startDate + duration.
2. Update unit tests to validate the startDate and endDate after project creation

[vikasrohit]

@RishiRajSahu we won't need to update the add phase endpoint because at that its the caller who sends the data for the phase, so caller can send the dates as required.

[architectt1]

#138

[vikasrohit]

Working fine for the specified requirements.