Proposal: query path tenancy (thanos-io#6320)

* Add 1st version of query path tenancy proposal

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Update proposal after initial feedback

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Add cool picture

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Include example in cross tenant query complications

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Improve reasoning for why not using the QFE

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Improve writing in "How" section

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Fix owner profile link

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Saswata Mukherjee <saswataminsta@yahoo.com>
Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Address few more PR review comments

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Address feedback on flag name text

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Update diagram

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Improve non-goals text

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Update diagram

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Update docs/proposals-accepted/202304-query-path-tenancy.md

Co-authored-by: Filip Petkovski <filip.petkovsky@gmail.com>
Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Clarify scenario for pitfalls of current solution

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Clarify that Store doesn't care about tenant label

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Add an action plan

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Mention alternative idea of modifying Store API

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Fix typo

Co-authored-by: Giedrius Statkevičius <giedriuswork@gmail.com>
Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Address lots of feedback on the proposal

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Format query path tenancy proposal doc

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Add a "Tenancy Model" subsection to "Goals"

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Mention header semanthics in comparison with gRPC message field

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

* Improve action plan structure and writing

Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>

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Signed-off-by: Douglas Camata <159076+douglascamata@users.noreply.github.com>
Co-authored-by: Saswata Mukherjee <saswataminsta@yahoo.com>
Co-authored-by: Filip Petkovski <filip.petkovsky@gmail.com>
Co-authored-by: Giedrius Statkevičius <giedriuswork@gmail.com>