Move all supporting entities endpoints under `/v4/projects/metadata`

[vikasrohit]

As of now we are hosting all supporting endpoints as root endpoints parallel to the /v4/projects e.g.

• /v4/projectTemplates
• /v4/productTemplates
• /v4/productTemplates/123/milestones
• /v4/projectTypes
• /v4/productCategories

we need to move them to

• /v4/projects/metadata/projectTemplates
• /v4/projects/metadata/productTemplates
• /v4/timelines/metadata/milestoneTemplates?reference='product'&referenceId=123 (Please note it is using timelines as root entity because milestone and their templates more relates to the timeline than projects and this new location of endpoint would also require the way it behaves. Now it would not provide milestone templates with path param, rather it would ask for 2 new query params reference and referenceId and would search the milestone templates for those two params)
• /v4/projects/metadata/projectTypes
• /v4/projects/metadata/productCategories

Also, we need to create a new endpoint which returns all the metadata as GET /v4/projects/metadata which would be public endpoint and would return all of the above endpoints' data without any filter.

[ngoctay]

Regarding to the 3rd one /v4/timelines/metadata/milestoneTemplates?reference='product'&referenceId=123

We also need to change the table name "product_milestone_templates" to "milestone_templates", right?

[vikasrohit]

Yes, but we kept that part as separate issue for better tracking. So you can finish that first and then come back to this.

[vikasrohit]

Closing. @gondzo please feel free to tag it as per convenience for payments.