Add more validation for free-form server fields (#272)

<!-- Provide a brief summary of your changes -->
The changes are intended to create validators for all the free-form
fields. Please find the details of the validation of different field
below.

- Repository.Source: only github and gitlab is accepted.
- Repository.Url - It should be a valid github or gitlab URL. Created
regex for both.
- Server.Name - Max 200 char can be there. Reverse domain name
verification is part of another PR (not owned by me).
- Package.Name - Max 200 char and no spaces.
- Server.Description - Max 100 char.
- Remote.Url - It should be valid URL.

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The motivation was to make the code clean and add base code for more
validator for different objects like Repository etc.
https://github.com/modelcontextprotocol/registry/issues/97

## How Has This Been Tested?
It's tested via UTs. Added UT's for all the validations.

## Breaking Changes
Yes

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

Co-authored-by: Avish Porwal <avishporwal@microsoft.com>
Co-authored-by: Adam Jones <adamj+git@anthropic.com>

internal/validators/utils.go

@@ -0,0 +1,50 @@
+package validators
+
+import (
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+var (
+	// Regular expressions for validating repository URLs
+	// These regex patterns ensure the URL is in the format of a valid GitHub or GitLab repository
+	// For example:	// - GitHub: https://github.com/user/repo
+	githubURLRegex = regexp.MustCompile(`^https?://(www\.)?github\.com/[\w.-]+/[\w.-]+/?$`)
+	gitlabURLRegex = regexp.MustCompile(`^https?://(www\.)?gitlab\.com/[\w.-]+/[\w.-]+/?$`)
+)
+
+// IsValidRepositoryURL checks if the given URL is valid for the specified repository source
+func IsValidRepositoryURL(source RepositorySource, url string) bool {
+	switch source {
+	case SourceGitHub:
+		return githubURLRegex.MatchString(url)
+	case SourceGitLab:
+		return gitlabURLRegex.MatchString(url)
+	}
+	return false
+}
+
+// HasNoSpaces checks if a string contains no spaces
+func HasNoSpaces(s string) bool {
+	return !strings.Contains(s, " ")
+}
+
+// IsValidURL checks if a URL is in valid format
+func IsValidURL(rawURL string) bool {
+	// Parse the URL
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		return false
+	}
+
+	// Check if scheme is present (http or https)
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return false
+	}
+
+	if u.Host == "" {
+		return false
+	}
+	return true
+}