[MVC] - Add new sidebar location for Exploring GitLab

Problem to solve

As we introduce a new section in our product for "Your work", there are some items in there that do not make sense to be included as tabs within those pages (ex: "Explore projects" on Projects page). It would be better to have one location/section within GitLab for exploring content that is not "yours".

Additionally, non-logged in users have access to the Projects, Groups, & Snippets pages, but do not currently have a sidebar. This makes it more difficult to explore across objects.

Proposal

Create a section in our navigation named "Explore" where users can go to search and discover various things within GitLab.

Resources

• Figma File
• Prototype

Changes included in this

Relocating tabs from "Your work"

• Projects page – Move "Explore" to be the first item in new "Explore" section (no longer as a Tab)
  • This will have the existing tabs for "All", "Most stars", & "Trending"
• Projects page – Move "Topics" to be within the "Explore" section (no longer as a Tab)
  • Nested navigation within Topics (ex: clicking on a Topic) should maintain the user within the Topics page, while showing the nesting through our site architecture (breadcrumbs & URL)
• Groups page – Move "Explore public groups" to be within the "Explore" section (no longer as a Tab)
  • Note: No tabs will exist under Explore Groups on this new page, only the current Filter (search by name) and Sort options
• Snippets page – Move "Explore snippets" to be within the "Explore" section (no longer as a Tab)
  • Note: No tabs, filters or sorting will exist under Explore Snippets on this new page (as that functionality isn't provided today for this content)

General Explore section guidelines

• For the breadcrumb, the first item would be "Explore" when on a page in this section (which would navigate to the first page within the section – Explore Projects)
• Page Titles should be prepended with "Explore" to help reiterate and differentiate that you are within the Explore section.
• Use the labels icon for the Topics item within the left navigation
• Title of this section in the Context Switcher would read "Explore"
  • Use the compass icon for the avatar/icon for this section
• Include the "New" (create) buttons for the various explore pages, which would direct to the "Your work" section (based on which type of content) as we do for the global create links within the create new menu

Updating pages where Tabs were removed/relocated to the Explore section

• Groups page – since this will now only contain 1 tab ("Your groups"), the Tab can be removed since it will be the only view.
• Snippets page – since this will now only contain 1 tab ("Your snippets"), we will no longer need Tabs at this level. However, the "All", "Private", "Internal", & "Public" tabs will now be the top level Tabs (nesting is no longer needed)

Additional improvements (may warrant splitting out)

Split out to a new issue here

• Project page – with the removal of 2 of the tabs on this page, we can eliminate the current nesting for the "Yours" Tab ("All" & "Personal") and include those as Tabs at the top level .
• Projects & Groups pages – For better layout consistency (matching pages like Issues, MRs, To-Dos), as well as to handle responsive better, move the Filter and Sort options to be within their own row/section directly above the results (underneath Tabs when present).
  • Refer to designs below for styling
• Remove the unnecessary line break (border) directly under the Page Title on the pages in "Your work" (and make sure to not include this line break on "Explore" pages) - Handled in !114017 (merged)
• Issues page – Update the "Subscribe to RSS feed" and "Subscribe to calendar" buttons to be icon-only buttons with a tooltip (similar to how we handle this on the Issues page within Groups/Projects.

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